Core Audio is not available in GarageBand
You are here because you have just exported a ringtone from MusicToRingtone to GarageBand and you get a "Core Audio is not available" alert and can't set it as a ringtone.
Don't worry it seems like it's an iOS bug and all you have to do is to restart your phone.
Here is the Apple support document if you are interested.
#MusicToRingtone #FreeRingtoneForiPhone #CoreAudio #GarageBand