Internet service and VoIP

I recently experienced the issue many here are having. My VoIP provider is Callcentric. I have an OBi110 ATA. It has been working without any changes for a long time, first when I had Xfinity home internet and after I switched to T-mobile 5G Home Internet last year, it was also working fine with the original configurations until recently. My old ATA configurations used a callcentric.com domain. I decided to check callcentric documentation for configuring OBi110/202 devices and noticed the domain they have in their documentation is sip.callcentric.net along with a few other configurations that I did not have (e.g. setting the outbound proxy), so I made all the changes recommended in the callcentric documentation in my ATA and my service is working again. I know when my ATA  was configured with the callcentric.com domain for a while it also worked with TM Home Internet, so I do believe it is likely some recent T-mobile changes and not the VoiP provider is the root cause of the service not working. Checking and experimenting with your ATA configs might help to get you service working again over TM Home Internet. ¡Buena suerte!