FaceTime suddenly dropping incoming & outgoing calls upon picking up

Daughter has old iPhone w/o SIM card to text & FaceTime w friends while at home on our WiFi. Has been working just fine but all the sudden, any FaceTime call, incoming or outgoing, drops immediately when answered. WiFi is fine and FaceTime works with no issues on other phones in the house. It’s just my daughter’s phone with the FaceTime issue. Texts still work fine on her phone.

Tried hard reset on the phone, resetting WiFi settings on the phone and reset the router, plus every setting we can think of on the phone with no luck.