Corrupted Sound of instrument
I installed the program today and after half an hour a file got corrupted and from that moment every file opened with musescore 4 no longer produces the sounds of the instruments but a very high sound. if I open the same file from musescore 2 or 3 the problem does not arise
Comments
A score from Mu4 can't get opened by Mu2 or Mu3 at all, so at least that part of your post seems wrong
But try Help > Revert to factory settings