Does anyone else have problem with Facetime calls in El Capitan? There's always a message "Remote User Does Not Exist". It works from iPhone (iOS 9) but not from Mac. Also Facetime Audio calls are endet immediately after calling...
10.11 facetime calls don't work
Just wanted to confirm that you are not the only one. Also, if two different contacts have shared data... when you make a call to one, it will show the contact name of the other contact. It is the WWDC beta afterall.
Workaround to this is to remove the contact and enter their details manually, or disable/re-enable contacts.