audio not playing in playback & MOV audio not exported

hello,

I have 2 issues:

1. the audio is not playing in playback mode. The added audio file however is added & played when I export the video.

2. The audio from the movie clip (.mov file) is visible in the preview mode (so I see the audio lines) but not included in the video export.

Due to issue 1 I obviously can't hear any audio in the playback.
When I check preferences ; video output & input it says "Speakers xxx (not working)"; but I dont' have any other option to select there,.

Thanks for your help!