FaceTime Failed: Person Not Available Consider an iPad 2 using WiFi attepting to make FaceTime calls to users on an iPhone 4. Each contact has their phone number defined under the iPhone tag (as opposed to Mobile). 

Whenever attempting a FaceTime connection, FaceTime attempts to connect, and fails with the error:


  FaceTime failed - 'Person' is not available for FaceTime.


Measures attempted:


close FaceTime from running apps.
disable &amp; re-enable FaceTime from Settings.
confirmed the device's WiFi is active &amp; enabled.


I've seen the 'solution' of "reset all settings", but suspect that's overkill, and likely won't work, as reported by lots of other users.

How can this error be avoided?
According to Apple, some of the symptoms are:


When you are calling someone on FaceTime, the number on their screen
is not your number.
People are unable to initiate a FaceTime call
with you. 
After installing a new carrier settings update, FaceTime
does not activate.


How to fix:


In Settings > Phone, turn FaceTime OFF and turn it back ON again
Go to Settings > General > Reset > Reset all settings
Done