Nothing has changed on my phone since yesterday. In the screenshot above - my Alexa Presence and Life360 Presence are also phone-geofencing dependent, and they continue to work. And I haven't installed any new apps on my phone. Several apps were updated during that time, but I don't believe the Hubitat app was one of them.
What should I try? Delete app data & cache? Remove/re-install?
I haven't noticed any problems recently, but after reading your post, I looked at the Debug Information in the mobile app and saw several errors for yesterday and this morning. There was always a successful geofence api posting within 10 seconds of an error, so maybe that's why I hadn't noticed.