Today my father was playing with FaceTime and couldn’t reach me which was odd as my phone was on and had WiFi access. My dad had tried earlier using my email address as well and when I looked at my iPad later, I saw a missed call, but it should have rang on my desktop. The number on my iPad was the number that my dad’s phone was initially given before he ported his phone number.
Ahh, a bell went off and after a bit of searching, I came across an Apple Support Article about this particular problem after porting. After reading this, it dawned on me why I couldn’t FaceTime from my desktop to my iPhone; I had ported my phone number to AT&T a few weeks ago (I was just forwarding it from Sprint since I got my phone last year). The quick fix was to turn off FaceTime and turn it back on again to get it to re-register with Apple’s servers. My dad did the same thing and presto, FaceTime worked.
However, I also forgot to setup FaceTime on the desktop with my primary email address (my Apple ID is not my primary email address). A trip to the FaceTime preferences on the desktop fixed that issue as well.
So, if FaceTime isn’t working, check preferences and turn it off then on again and it should work again.
As you can probably tell, I don’t use FaceTime much!