If you have connection or sound quality issues with FaceTime
If your cellular connection or Wi-Fi network are running slow, or other users are streaming audio or video on the same Wi-Fi network, you might have these issues:
Connection alerts or unable to connect
Choppy video calls
Black screen
Dropped calls
Make sure that both you and the person that you're calling are using a fast Wi-Fi or cellular connection. If you’re using Wi-Fi, FaceTime requires a broadband connection.