Running macOS High Sierra 10.13.2 on latest MacBook.
1. Direct A/B comparison with v1.3 on the same computer with various score files: 1.3 works fine; 2.x (26 Dec) is silent.
2. No error message - just silence.
3. The metronome sounds fine - it's just the score notes that are silent.
Comments
See https://musescore.org/en/node/267914
According to that thread solved after a Reset to Factory defaults.