I recently had a problem trying to place calls with the Facetime app on my Apple devices that had Norton VPN installed. I made a connection to an individual at an out-of-state campground on one day, but two days later, I tried calling the same individual at home and the calls failed. It would ring on at both ends, but we could not establish a connection. Facetime would say "connecting" and then "connection failed". They would try to call back, I would get the message that someone was calling, but the connection would always fail. I contacted Apple Support, and to make a long story short, I ended up having to remove Norton VPN from my devices as turning it off did not solve the problem. Apple Support seems to think that there possibly could be a bug or glitch in VPN. I had no problems until after the previously mentioned call. Has anyone else had this problem? Are there any suggestions?
If turning off the Norton VPN did not resolve the issue, it should not be involved with your issue. Do you also have Norton Mobile Security, NMS, on your device? If so, there have been some connection issues with the Web Protection feature of NMS.
Try reinstalling the VPN, and try to Facetime again. If you still have the connection issues, disable the Web Protection feature of NMS and leave the VPN turned on. Then test the Facetime again. If this resolves the connection issue, let me know and I'll give instructions to send logs to Norton from NMS.