Your Facetime not working may be attributed to the following reasons. First, this program hasn't been updated to the latest version. The second reason is the incorrect Date and Time settings. And there might be also the system errors. To fix this issue, you can first update the latest Facetime or go to "Settings" > "General" > "Date & Time" to correct it. If the problem is still not solved, you can try using iOS system repair tools. If you have some questions, be free to give a reply.