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, M-Audio Midisport 2x2 and keyboard. Somehow after using it for a while (weeks) the playback controls, mixer and synthesier were disabled (grayed out) so I can't play back scores. I use that to check what I am inputting. It first occured after I connected my MacBook to a friends soundcard, maybve that's got something to do with it?

Fixes I found here in 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. I worked again! But after a while (hours), with no apparant reason, the issue returned.

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.