Visual Voicemail In The Phone's App

Several CalyxOS updates ago, probably last year, there was an update that listed, 'we added more carriers to VVM.' In that update, my VVM in the phone's app worked perfectly, that was until the next month's update and I have never been able to get it to work since. After numerous attempts to re-activate VVM, it always displays 'Activating visual voicemail'..and never does.

I switched to a new carrier and the same thing happens with them. Is this a Calyxos issue? I am on a Pixel 4a5G and can only use AT&T's Visual Voicemail app to get my VVMs.