For posterity, I had to:
- Go into Settings in the mobile app
- Select “Companion App” from the menu
- Tap on my server at the top of the screen
- Change “Device Name” to what it used to be (i.e.,
notify.mobile_app_DEVICE_NAME_HERE
) - Exit settings
- Force-close and restart the mobile app
I was then able to go into Developer Tools → Services and confirm the expected notification service was available.