Got my new M4 Max MBP14 yesterday. Migration from my old MPB14 went smoothly, everything worked, with one exception: All Reminders were gone. Reminders just displayed a blank frame with nothing in it at all: No left panel with lists or tags, no reminders. Everything just white.
I worked on this for 24 hours and finally found a solution:
- Quit the Reminders app
- Settings → iCloud → See All → Turn off Reminders
- Go to ~/Library/Reminders/Group Containers, then rename group.com.apple.reminders or delete it (and then empty the trash)
- Activity Monitor → Force Quit → remindd
- Back in Settings, re-enable Reminders
- Start the Reminders app → Voila!
Kudos to this discussion on Reddit to get me on the right track.