Custom audio to play on top of score

I recently uploaded a score using a plugin (Spitfire Audio's LABS soft piano) and I don't know if musescore doesn't read the plugin properly or whatever but the audio is all bugged when I post it. The pedal won't work in some places even though I've added pedal markings in the score itself. The weird thing is that it sounds fine in the musescore app (I'm on pc) and the audio is working and the pedal works as it should. As soon as I upload the score onto musescore.com, however, the pedal starts bugging out all over the place. I uploaded two scores (two versions of one song, both using the same plugin) and they are both not working in different places. Anyway, if any of you know what's happening, or until I can find a solution to it, is there a way to upload an mp3 (not from youtube) to play over the score? That way the score sounds as it should.

Sorry for the huge paragraph of me not explaining clearly. Thanks in advance.