FWIW, I recently set up an iPad for a friend's dad, so he can connect with his grandkids. No **** way would that thing make a call, and the UI for Facetime is minimal to the extreme (i.e., to the degree of uselessness). It's an app that should "just work" but **** well doesn't. (IMHO, they ruined everything when they transitioned from iChat to Messages or iMessage or whatever the heck it devolved into).
He's signed into iCloud. Open FaceTime. Enter the recipients FaceTime address (in this case, my own for testing purposes) and... what? There's no obvious activity, no spinning "activity" indicator. There's an "Audio" button in blue that does nothing when clicked, and a Video button greyed out.
You sit there and stare at yourself as the camera eyes you, and wonder... what am I supposed to do next?
FaceTime works as it's supposed to on my iPhone with other people, so perhaps it's just his iPad being wonky.
My working theory, based on an earlier experience just like this, is that FaceTime's authentication servers are slow on the uptake. We had created an iCloud account for him just an hour or so prior. While he could log-in to iCloud and access its services, FT just would not connect. Although - as I said - in the absence of any activity indicator or error message, we have no way of knowing if FaceTime is even trying to do something.
Bad. Design.