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)