Nothing is more frustrating than setting up an Expert Advisor only to find it isn't trading. I've worked through these same EA issues more times than I can count, and it's almost always one of a handful of culprits. The good news: 95% of common EA problems have a fix that takes less than a minute. This guide covers every issue I've run into, ordered from most common to least, with exact steps for each one -- plus the less obvious problems that tend to show up weeks or months into running an EA, like disconnections and backtest-versus-live mismatches.

Most of what follows applies to any Expert Advisor on MT4 or MT5, not just a specific product. Automated trading removes emotional decision-making from execution, which is exactly why platforms like MetaTrader's MQL5 documentation exist -- the terminal itself generates specific, loggable error codes for almost every failure mode, and knowing how to read them saves a lot of guesswork.

Problem 1: EA Not Trading

This is the most common issue by far. The EA is loaded on the chart, but it never opens a trade. Here's the fix, step by step:

Checklist: EA Not Trading

Go through these in order. The first three items alone clear up about 80% of "EA not trading" cases.

Reading the Experts Log Like a Pro

The Experts tab (Terminal > Experts) is the single most useful diagnostic tool MT4 and MT5 give you, and most traders never open it until something breaks. Every action the EA attempts, and every reason it fails, gets logged there in plain text. Learning to read a handful of recurring messages will resolve most "why isn't this working" questions faster than any forum post:

These correspond to standard MetaTrader trade server return codes -- the full reference lives in the MQL5 documentation if you want the exhaustive list, but the six above cover the vast majority of real-world cases.

Problem 2: Sad Face Instead of Smiley

A sad face next to the EA name means it's loaded but blocked from trading. It's a permissions problem, every time:

Fix for Sad Face

• Step 1: Go to Tools > Options > Expert Advisors tab
• Step 2: Check "Allow automated trading"
• Step 3: Check "Allow DLL imports" if the EA requires it
• Step 4: Click OK
• Step 5: Right-click the chart, go to Expert Advisors > Properties
• Step 6: On the Common tab, check "Allow live trading"
• Step 7: Click OK -- the face should change to a smiley

If the face is still sad after all that, pull the EA off the chart and re-attach it. MT4 sometimes needs a fresh attachment before it picks up the permission changes.

MT5 handles this slightly differently: instead of a smiley/sad face icon, it shows a status indicator in the top-right corner of the chart, and the "Algo Trading" button lives in the main toolbar rather than being called AutoTrading. The underlying settings are the same -- Tools > Options > Expert Advisors still governs whether automated trading is allowed globally, and the per-chart Properties > Common tab still needs "Allow algo trading" checked. If you're moving a setup from MT4 to MT5, expect to click through this permission screen again even if you already enabled it on the other platform; the two terminals don't share settings.

Problem 3: Wrong Lot Sizes

The EA is trading, just not with the lot sizes you expected. It's usually one of these:

• Auto lot sizing: the EA scales lot size off your account balance, so a balance change shifts every trade size with it
• Risk percentage set too high: even a 2% risk input can produce large lots once the account balance grows, so check the EA's risk parameter
• Fixed lot setting: the EA may be locked to a flat lot size that no longer matches what you intended
• Broker lot restrictions: your broker's minimum, maximum, or step size for lots may differ from what the EA assumes

To fix it, open the EA's properties (right-click chart > Expert Advisors > Properties > Inputs tab) and adjust the lot size or risk percentage. For more on getting this right, see our position sizing calculator.

How Auto Lot Sizing Actually Works

Most percentage-risk EAs use a version of the same underlying formula: they take your account balance (or equity), multiply it by the risk percentage you set, then divide by the stop-loss distance in points to arrive at a lot size. So a $2,000 account risking 1% per trade with a 200-point stop loss produces a much smaller lot than the same account risking 3% with a 50-point stop. This is standard position-sizing math used across algorithmic and discretionary trading alike -- Investopedia's guide to margin covers how that lot size then translates into the margin your broker holds against the trade. If lot sizes look wrong, the input worth checking first is almost always the risk percentage or fixed-lot field, not a bug in the EA itself.

Problem 4: License and Authentication Errors

Most commercial EAs verify licenses against your account number, MT4 installation, or hardware ID. Here's what the common error messages mean and how to fix them:

Licensing exists to protect legitimate vendors from having their EAs copied and resold, so a certain amount of friction here is normal and not a red flag by itself. What is a red flag: a "vendor" who can't explain why an account or hardware ID is tied to a license, who demands payment through untraceable methods to "unlock" a purchase you already made, or who pressures you to bypass license checks entirely. The FTC's guidance on investment scams is worth a read before buying any EA from an unfamiliar seller, and our own EA red flags and scams guide covers the specific warning signs to check for in this space.

Problem 5: Connection and Server Issues

If the bottom right corner of MT4 shows "No connection" or "Invalid account," the EA simply can't function:

• "No connection": check your internet connection, switch to a different broker server (File > Login), or just restart MT4
• "Invalid account": re-enter your login credentials through File > Login to Trade Account
• "Trade context busy": another EA or script is already running. Wait it out, or remove the conflicting EA
• Frequent disconnections: this usually points to an unstable internet connection. Consider a VPS for stable connectivity

A home internet connection, even a good one, isn't built for 24/5 uptime -- ISP maintenance windows, router reboots, and power blips all interrupt a locally-run terminal. Running MT4 or MT5 on a VPS close to your broker's trade server removes most of this category of problem outright, since the terminal keeps running whether or not your own computer is on. MetaQuotes publishes its own MetaTrader VPS service as one option, though any reputable low-latency VPS provider works; the goal is consistently low ping to the broker's server, not a specific brand.

Problem 6: Symbol Not Found or Mismatch

Brokers don't agree on symbol names. Your EA might be coded for "XAUUSD" while your broker lists the same instrument as "XAUUSD.r" or just "Gold":

• Check Market Watch: right-click Market Watch and select Show All to see every available symbol
• Find the exact name: note the exact symbol name your broker uses, suffixes included
• Update the EA: many EAs let you type the correct symbol name into the input parameters
• Contact support: if the EA has no symbol input at all, reach out to the developer directly

The suffix itself usually tells you something about the account type -- a ".r" or ".a" often marks a raw-spread or ECN-style account variant at the same broker, rather than a different market. Since gold (XAU) is quoted against the US dollar as a spot-style CFD by most retail brokers rather than traded as a listed futures contract, there's no single universal ticker the way there is on an exchange. If you want to see how the underlying market itself is quoted and tracked outside the CFD layer, resources like the World Gold Council's Goldhub and CME Group's gold futures data are useful reference points, though your EA will always trade whatever symbol your specific broker lists.

Problem 7: EA Performing Worse Than Expected

If the EA is trading fine but the results fall short of what the developer advertised, look at these first:

• Spread too wide: your broker might be quoting a 30-40 point gold spread when the EA was built around 10-15 points. Try an ECN broker
• Wrong timeframe: an H4 strategy run on M15 will behave nothing like it was designed to
• VPS latency: slow round-trip time between your VPS and the broker's server shows up as slippage
• Market conditions changed: a strategy tuned for trending markets tends to struggle once price starts ranging, and the reverse is true too
• Over-leveraged: oversized lots turn every losing trade into a bigger dent in the account. Our risk management guide covers this in depth

Problem 8: EA Stops Trading After Running Fine for Weeks

This one catches people off guard because nothing appears to have changed. The EA worked correctly for days or weeks, then one morning there are no new trades and no obvious error on screen. A few causes account for almost every case:

• VPS or terminal disconnected silently: the connection dropped and MT4/MT5 never automatically reconnected. Check the bottom-right corner for "No connection" and reboot the terminal if needed
• Windows updates restarted the VPS: most VPS providers apply patches on a schedule, and if MT4 isn't set to auto-launch on startup, the platform stays closed after a reboot until someone opens it manually
• Broker changed server address: brokers occasionally migrate to new trade servers. Go to File > Login to Trade Account and check whether a new server appears in the list
• AutoTrading got toggled off: a platform update, a misclick, or another script running on the same terminal can silently disable the AutoTrading button
• Chart got closed or the EA got removed: double-check the chart still shows the EA name in the top-right corner with a smiley face, not just an empty chart

The fix for all of these is really about detection speed rather than the fix itself, which is usually a simple restart or re-login. Setting up VPS uptime monitoring so you get an alert the moment the connection drops turns a multi-day gap in trading into a five-minute fix.

Problem 9: Backtest Results Don't Match Live Trading

This is less a "problem" with a single fix and more a structural reality of how backtesting works. A backtest replays historical price data through the EA's logic in a simulated environment; live trading executes real orders against a real broker's real liquidity. Those two things will never match perfectly, and understanding why keeps expectations realistic:

• Spread modeling: most backtests use either a fixed spread or a simplified historical spread series, while live spreads widen and narrow throughout the day, especially around news and session opens
• Tick data quality: MT4's strategy tester historically relied on generated ticks rather than true historical tick-by-tick data, which can smooth over exactly the kind of price spikes that cause slippage live. MT5's tester improved on this significantly
• No requotes or execution delay in most tests: a backtest usually assumes instant, guaranteed fills at the requested price, which real market execution doesn't offer
• Different market regime: if the backtest period was more trending or less volatile than current conditions, results diverge regardless of how well the code was tested

Investopedia's overview of backtesting covers these limitations in more general terms, and they apply to any automated strategy, not just gold EAs. We go into far more depth on this specific gap in our backtest results vs. real trading guide -- it's worth reading before assuming a discrepancy means something is broken.

Preventing EA Problems Before They Start

Most of the issues above are fixable in minutes once you know what to look for, but a short setup routine prevents the majority of them from happening at all:

• Use a VPS from day one rather than switching after the first disconnection costs you a missed trade
• Confirm your broker explicitly allows algorithmic trading and is regulated by a recognized authority -- the CFTC's consumer protection resources outline what to check before funding any trading account
• Note the exact symbol name your broker uses for gold before you ever attach the EA, so a mismatch never happens in the first place
• Check the Experts log weekly, even when everything looks fine, since some warnings show up long before they cause a real problem
• Keep a record of your EA's license details (account number, purchase date, vendor contact) somewhere separate from the VPS itself, so a hardware reset request doesn't turn into a scramble