Audio
The audio in Musescore 3 has a lot of problems when played on speakers other than the computers. When I play it back on aux or a bluetooth speaker it still only plays on the computer or sometimes doesn't play at all. When I try exporting it into a mp3 file it just doesn't play at all.
Comments
press the MIDI-input toolbar button twice
See: https://musescore.org/en/node/300000#comment-973475
HTH