There are two types of MT5 accounts. Netting and Hedging.
The netting system allows having only one position per financial instrument meaning that all further operations at that instrument lead only to closing, reversal or changing the volume of the already existing position.
The hedging system allows you to have multiple positions per symbol, including oppositely directed ones.
Currently, our system works with hedging MT5 accounts that can open multiple trades on the same pair. If they are netting accounts, grouped into 1 position, it does not work.