When you install Skype for Business on Mac, version 16.28.175, in macOS Catalina or Mojave, Skype for Business is not able to use any input sources from the Mac for audio even though your audio device(s) are set accordingly in the Skype for Business audio/video preferences.

Skype for Business on Mac fails to prompt for access to the microphone. This unfortunately does not allow the use of any input source (built-in microphone, headset, desk phone) while using Skype for Business on Mac.

There is no known resolution at this time.

This problem has been reported to Microsoft, and hopefully they will resolve this problem soon.

Workaround #1

1) Create a new administrator account on the Mac.

2) Sign in to the Mac using the account created in Step 1.

3) Uninstall Skype for Business.

4) Reinstall Skype for Business.

Workaround #2

1) If you have access to a legitimate older version of Skype for Business on Mac prior to 16.28.175 that is compatible with your respective macOS version, install that first and hopefully it will prompt for access to the microphone.

2) Upgrade your Skype for Business on Mac to the latest version.

Workaround #3

This workaround involves adding information into the TCC.db file as described at https://answers.microsoft.com/en-us/msoffice/forum/all/skype-for-bussines-on-mac-os-catalina-10154-doesnt/973272f8-98d6-4dc3-8ae7-834cc4b9630b?rtAction=1587993601958. This will require an account on the Mac with administrative privileges and also require Terminal to have Full Disk Access.

1) Open Terminal.

2) Type the following command and press Return:

sudo sqlite3 ~/Library/Application\ Support/com.apple.TCC/TCC.db "INSERT or REPLACE INTO access VALUES('kTCCServiceMicrophone','com.microsoft.SkypeForBusiness',0,1,1,NULL,NULL,NULL,'UNUSED',NULL,0,1541440109);

Outcome

You will be able to use your microphone with Skype for Business.