AT&T Office@Hand Calls Going Straight to Voicemail

We have several users who have reported that recently calls going to their Office@Hand app are going straight to voicemail. Despite having the app running on their mobile device, and their laptop. No DND is set, no special call handling or forwarding rules are set. The only solution is that once this starts happening they have to reinstall the apps and it works fine for a few days, then triggers again.

This isn't happening to just one person, this is happening to multiple people. Has anyone else experienced this?