If you started to have issues making or receiving FaceTime calls after April 16, 2014, your device or your friend’s device may have encountered a bug resulting from a device certificate that expired on that date. Updating both devices to the latest software will resolve this issue.
If you’re using iOS 7.0.4 or later or iOS 6.1.6, this issue doesn’t affect you.
If you’re using these versions of OS X or FaceTime for Mac, this issue doesn’t affect you:
OS X Mavericks v10.9.2 or later
OS X Mountain Lion v10.8 with the latest security updates
OS X Lion v10.7 with the latest security updates
FaceTime for Mac version 1.0.5 or later for Mac OS X v10.6
The bug is due to a “device certificate that expired on that date”, referring to April 16, 2014. According to Apple, 11% of iOS users are still using iOS 6, while 87% of devices have updated to iOS 7.
Sounds like if you want to use FaceTime and you’re an iOS 7 holdout, it’s now time to upgrade. Is this a subtle way of Apple forcing iOS 6 users to update to iOS 7?