Reminders 'clear all' not working

Sometimes it needs a Push ( Reminders App. ) Internet Accounts >> iCloud and Uncheck Reminder from iCloud Sync on one device. Restart computer and re-Enable Reminders in iCloud and pause and Test.

Still not working - Sign Out of iCloud and again restart and log back into iCloud and paste and Test.

The two above is attempting to Nudge iCloud to sync across all devices.

Are the two devices Mac Pro and iPhone both signed into the same Apple ID and same iCloud Accounts plus all iCloud Options are enabled on both devices ??

Have found the Sync of Reminders on one device is often slow to sync across all devices.

Running MBA M1 Big Sur 11.5.2, iMac Catalina 10.15.7 and Mac Mini High Sierra 10.13.6 and iPhone 12 iOS 14.7.1 They almost never sync immediately.

Shot in the dark - user wrote " Mac osx 11.4 Big sur " is out dated. Most recent version is 11.5.2 and may or may not be related to your issue.

Hi elastic, 

Thank you for posting in Apple Support Communities.

Using Reminders is so convenient, so let’s see if we can help find out what’s going on when they pop up in the Notification Center.

Take a look a Use Notification Center on Mac in the section “Use notifications in Notification Center on your Mac”. The last bullet point describes clearing all. Try turning off Reminders for notifications and turning it back on to see if that will make a difference.

If turning the notifications off and back on doesn’t resolve the behavior, reach back out and let us know does the same thing happen on your other devices when trying to clear all at once.

Take care!