This is a known issue and has been around for a while. I am not sure if the problem lies within ProfitUI (unlikely) or was induced with one of SoE's patches (most likely)
The problem seems to stem from the fact that if you have any of the Pots in either your house vault or bank, Profit is directed to use them first! regardless of whether you have them in your inventory.
There are 2 usable workarounds for this problem :-
1/ Make sure your house/bank slots do not have any Pots in them and the C2C function will work as expected.
2/ Open up a new hotbar and place your Pots from inventory onto the hotbar and use them from there.
I hope that helps until a soloution is found