Zuerst dies probieren (prüfen, ob der User auch alle rwx-Rechte hat):

Dann im Terminal tccutil reset Camera bzw Microphone ausführen (ev vorher csrutil disable – see below – in Recovery durchführen):


Schlißelich im RecoveryMode booten

Terminal öffnen:

csrutil disable

Danach neustarten und wieder ins Terminal:

Manually manipulate the security database TCC.db:

1 Open Terminal
2 Make a backup copy of the ~/Library/Application\ Support/com.apple.TCC/TCC.db file
3 Open the database by giving command: 

sudo sqlite3 ~/Library/Application\ Support/com.apple.TCC/TCC.db

4 Provide your password when requested
5 Within sqlite3, For Skype for Business audio fix type in command:

REPLACE INTO access VALUES('kTCCServiceMicrophone','com.microsoft.SkypeForBusiness',0,1,1,NULL,NULL,NULL,'UNUSED',NULL,0,1541440109);

6 Type .exit to exit the sqlite3
7 Skype for Business should be visible in the  Security & Privacy preferences Privacy-Microphone view 

This is not something the user should be required to do, but until the application is fixed, this might be the only way. 
For me any other method (reinstall, NVRAM reset) didn’t help.

Am Schluss mit CMD+R im Recovery-Mode booten

Terminal öffnen:

csrutil enable