If you post the Pronto Hex for some working command of that device (such as rewind) we can identify the codeset and tell you the Pronto Hex for FF. (I won't have access to the files I'd need to do that until Monday. But someone else may answer sooner).

It also would be interesting to see the Pronto Hex of the attempt to learn FF where the Pronto said OK but the result didn't work.