MT4 · Runtime errors
MT4 4020 · Expert function calls are not allowed | YI GOLD
ERR_EXTERNAL_CALLS_NOT_ALLOWED
Official meaning
Expert function calls are not allowed
Possible causes · YI GOLD suggestions
Determine the cause from the official meaning, the triggering function and terminal logs.
Troubleshooting · YI GOLD suggestions
Inspect terminal logs and the failing function return value. Check inputs, array bounds, resources, connectivity and required permissions against the official description.