Why is FaceTime not dialing for a specific contact on iPhone?

whenever i try to call a specific contact via facetime, it doesn’t dial. it says its calling but the other person never received it on their end and there is no noise indicating it was dialing. i’ve tried other ways to facetime, through the actual facetime app, messages, phone app (call log/contacts) but it just shows the screen as if im calling them but it doesn’t actually dial. when it first happened i hung up on the person (facetime) to call another (regular call), planning to call the previous person through facetime again. i did this 2-3 times going back and forth then around my 4th time it stopped dialing on facetime even though my other calls worked perfectly fine. does anyone know whats wrong and how to fix it?

[Re-Titled by Moderator]