Summary: EA fails to run on MT4 due to ‘No Expert Advisors allowed’? Enable AutoTrading in Options, switch on the toolbar button, and disable safe mode to fix it.
Step 1: Enable AutoTrading in Global Settings
Open MT4. Click ‘Tools’ → ‘Options’ (Ctrl+O). Go to the ‘Expert Advisors’ tab. Check the box ‘Allow automated trading’. Also check ‘Allow DLL imports’ if your EA requires it. Click OK. Screenshot: Options window with Expert Advisors tab and both boxes checked.
Step 2: Turn On the AutoTrading Toolbar Button
Look at the top toolbar. Find the ‘AutoTrading’ button (green play icon or smiling face). If it is red or crossed out, click it once to turn it green. You will hear a voice confirmation ‘AutoTrading enabled’. Screenshot: toolbar with green AutoTrading button highlighted.
Step 3: Disable Safe Mode for Individual Charts
Right-click on your chart. Select ‘Expert Advisors’ → check that ‘Disable’ is NOT selected. Also uncheck ‘Enable Safe Mode’ if it appears in your MT4 version. Then drag your EA onto the chart again. The EA smiley face should turn from gray to green. Screenshot: right-click menu showing Expert Advisors options.
Reference: MetaQuotes official documentation – Enabling Automated Trading.