No sound on Big Sur

Hey everybody,

I recently upgraded to Big Sur on my Mac, and tried to open some old scores of mine on Musescore
but there was no sound and no audio or midi device selection option.

Opened the preferences, reset all to default, restarted I/O audio and midi settings but no good...
Restarted the system a few times, uninstalled and installed again...
No progress, no sound options at all.

Any help?

Thanks in advance

Regards

John