Musescore 3 - OSX - Playback controls, mixer and synthesizer disabled, existing fixes not working

OS: macOS 10.15, Arch.: x86_64, MuseScore version (64-bit): 3.4.2.25137, revision: 148e43f
I updated to Musescore 3 recently. Have a very simple setup with a 2012 MacBook Pro running on OSX Catalina, M-Audio Midisport 2x2 and keyboard.

Somehow after using it for a few weeks the playback controls, mixer and synthesier were disabled (grayed out) so I can't play back scores or hear the notes I am entering.

The issue first occured after I connected my MacBook to a friends soundcard (I don't use an external soundcard myself), so maybe that's got something to do with it?

Fixes I found on the forum haven't worked (tried them all, really), so I reinstalled Musescore, but it did not work.

Eventually I reinstalled my OSX (Catalina) operating system, which did the trick. But after a few times of using Musescore the issue returned, with no apparant cause. I did not hook my MacBook up to an external soundcard or something like that, the controls were just grayed out all of a sudden.

I found that on the Preferences -> I/O page I cannot select any values in the PortAudio section. Fields are blank and no options to select are shown for API, Device, Midi Input and Midi Output.

I would really appreciate if anyone could help me get this fixed!

Thanks.