+1, the sending bank can only see that they sent it.....somewhere.....not that it reached your account
The investigation has to start from the sending bank side (this used to be my job many years ago). A trace id is not sufficient, ask them for a full copy of the payment message confirming the BIC & IBAN, amount & date/time......only by insisting on getting this will you have actual confirmation of what WAS paid rather than what they think they paid/should have paid.
Through digging that out the problem should come to light, if all looks correct with that then you bring that copy to the receiving bank and they then have something concrete to look for, which in fairness to them they don't have now. (In an ideal world you shouldn't have to do the legwork but in my experience sometimes you have to!)