The issue seems to have resolved itself. Last Thursday night, I got a avalanche of backlogged notifications, then Friday was business as usual.

Yes! Same here. Notifications magically started appearing again. I got an avalanche of them Thursday after hours, then Friday was back to business as usual.

Yes, I upgraded in late June and have been successfully using WF/Teams until Monday.

Around mid-day on Monday, July 21, I stopped received any updates or notifications in the Workfront app for Teams. Notification settings have not changed. Before I submit a ticket, has anyone else experienced this?