Can't unmute Skype for Business macOS

Hello,

I'm using Skype for Business as a guest, but when I join the meeting, I can't unmute myself. If, I manage to unmute myself the Skype for Business is crashing. If its not crashing it muted me automatically. I'm not able to use it or speak, I have the same problem with my video. I'm using macOS Catalina 10.15.4 and SkypeForBusinessInstaller-16.28.0.192.pkg. My Quicktime is up to date as requirements. I tried to reinstall and install again everything multiple times without success. Please let me know, if you need some logs.

Thanks,

Peter