Summary: This guide covers common reasons for MT4 EA loading failures and DLL errors. Follow clear steps to enable DLL imports, check file locations, and validate EA integrity.




Step 1: Check EA File Location and Installation
Ensure the EA (.ex4 or .mq4 file) is placed in the correct folder: MQL4/Experts (for MT4) or MQL5/Experts (for MT5). Use File > Open Data Folder to locate the directory. Incorrect placement often causes "EA loading failed."
![Screenshot: Data folder path and Experts folder location]

Step 2: Enable DLL Imports in EA Properties
Many EAs require external DLLs. Right-click the chart, select Expert Advisors > Properties, go to the Common tab, and check Allow DLL imports. Also check Allow live trading if needed. Unchecked DLL imports trigger "DLL call failed" errors.
![Screenshot: EA properties window with DLL imports checkbox highlighted]

Step 3: Disable Conflicting Security Settings
In Tools > Options > Expert Advisors, enable Allow automated trading and disable Disable automated trading when the account has been changed. For MT5, also check Allow WebRequest for listed URLs if the EA uses online data.

Step 4: Verify EA Compatibility and Compilation
For custom EAs, open the .mq4 file in MetaEditor (F4). Click Compile (F7). Fix any compilation errors. If the EA was created for an older MT4 build, update the code – deprecated functions like WindowExpertName() may cause loading failures.

Step 5: Restart Platform and Re-attach EA
After changing settings, restart MT4/MT5. Drag the EA from the Navigator panel onto the chart. In the pop-up, ensure Allow DLL imports and Allow live trading remain checked. The EA smiley face should appear – if not, check the Experts journal tab for specific error codes.

Reference: MetaQuotes Help Desk – "Expert Advisor not working" and "DLL imports" sections (https://www.metatrader5.com/en/terminal/help/algotrading/experts)