UA can do nothing about this as the partner airline has to authorize (and pay) UA for the credits. The first step is to get the partner to viod that credit to their program. While the partner can do this, there is little motivation for them to do that -- this may take many tries and may not work. If the partner airline does void the credit to their program, you can then request missing partner credit with UA.

This can be a frustrating process, good luck. Best to have the correct FF program on the ticket before flying the segment.