Facetime audio unavailable

[Kulfon]

Dear community, I started having issues with Facetime. People cannot call me and I cannot call people and I get this message - facetime audio unavailable. I am using an iPhone 6s with iOS 9.3.1.
Facetime is activated both for wifi and cellular. Everything else is working fine, just the facetime. Any clues?

 

[electronicsguy]

no, because there's insufficient info. nothing anyone can suggest except turn off/on, reboot, restore.