A Microsoft Teams change is causing calls to go straight to voicemail, much to users’ happiness worldwide. Microsoft Teams administrators can track this incident under TM261472 while Microsoft rolls out the fix. Users worldwide look at this as a Friday gift instead of a bug that is being fixed as a feature. The fix is being rolled back and admins can track the bug under the admin center of Microsoft 365 Status while the fix is implemented in the next few days. The bug was isolated by a recent change that has caused some of the infrastructure to send some Microsoft Teams calls straight to Voicemail.
Source: https://www.bleepingcomputer.com/news/microsoft/friday-gift-microsoft-teams-bug-puts-calls-directly-in-voicemail/