Why can't I group facetime? I can't add more than one person.

Whenever I try to do a group facetime call, I can search and add one person, but when I try to add a second, they are always grayed out.

All devices are iphones and are iphone 8 or above, all with latest updates etc. All can facetime each other individually, but I can never create a group facetime.

I have tried this in iOS 12 and even after iOS 13 it still will not work as a group on any/all of the devices.

I restarted, restored, formated, disabled and re-enabled facetime. I have tried every option I can find.