Error 4752 usually appears when auto trading is not fully enabled. If it's not fully enabled mk cannot send the order to the broker.
How to fix
- Make sure auto trading for the expert advisor is enabled from the window that appears when adding the EA to the chart
- Make sure the general auto trading switch is enabled from the top bar, AutoTrading button
How to know if fully enabled
- MT4 there should be a smiling face in the top right corner of the chart
- MT5 there should be a green play button in the top right corner of the chart
MQL5 error codes