Error 4109 — Trade Is Not Allowed is a frequent error that occurs when using expert advisors in MetaTrader 4. This means that the EA cannot place or modify orders.

This error can be fixed by enabling automated trading in the MT4 options and enabling live trading in the EA’s properties.

You can follow our documentation article on Enabling Auto Trading in MT4. 

In rare cases, this might be due to the broker disabling trading for specific trading accounts or account types.

In case your broker doesn't allow EA trading, you will continue receiving error 4109 when your EA attempts to place trades. This cannot be solved using options available in MT4 and you would need to contact your broker about this issue.