Voicemail asking for Password to access

My iPhone Xs Max version 14.6 has always had working Voicemail. Out of nowhere Voicemail is asking to Set Up a password to retrieve my voicemails. I've never had any Password for either Voicemail nor my iPhone. And when I try to enter a numbers Password: It says "Saving Password" followed by "Voicemail Error" Try again later. My only choice is to hit OK. When I called and left a message from another iPhone, I heard my recorded message and left a voice message. My iPhone never acknowledged there's a new Voicemail like before. My wife's iPhone is on the same account and Network (T-Mobile) and hers is working fine, so don't suggest anything about the carrier. What is going on? And how do I fix this?