Who is the calendar provider, e.g. Google, outlook.com etc., and how was it added to TB, e.g. built-in CalDAV or with an add-on?

I have Outlook/Exchange, Google, and iCloud calendars. Reminders don't work for any of them. I have subscribed to them through the Thunderbird calendar. I needed a soon-to-be-approved release of Provider for Google Calendar by Philipp Kewisch, which I got from the developer, to install the Google calendars. The Outlook calendar uses Owl for Exchange (I think).

Use the latest version of the Provider add-on, but only if you need to sync tasks. Otherwise, add the calendar as a CalDAV calendar. Same for iCloud, but use an app password. For outlook/Exchange, use latest TbSync and Provider for Exchange ActiveSync.

https://addons.thunderbird.net/en-US/thunderbird/addon/provider-for-google-calendar/

https://addons.thunderbird.net/en-us/thunderbird/addon/tbsync/

https://addons.thunderbird.net/en-us/thunderbird/addon/eas-4-tbsync/

You say use the Provider only if I need to sync tasks. How about events, or do you include those in tasks?

I've installed Provider for Google Calendar and unsubscribed and resubscribed to one of my Gmail accounts. Then I created a new reminder, but no notification popped up. Notifications were working until I upgraded to TB 136. Now I'm running 136.0.1 (aarch64). So I wonder if this is something happening with 136?

You probably didn't miss it, but just in case, this is happening on a MacBook Pro.

I'm going to try removing and resubscribing to all of the calendars to see if that fixes it...

Thanks for your help.

Removing and resubscribing using TbSync/Provider for Exchange ActiveSync for outlook.office365.com, Provider for Google Calendar for two different Google calendars, and the native New Calendar for iCloud did not help. Reminders still do not work.

You say use the Provider only if I need to sync tasks. How about events, or do you include those in tasks? I've installed Provider for Google Calendar and unsubscribed and resubscribed to one of my Gmail accounts. Then I created a new reminder, but no notification popped up. Notifications were working until I upgraded to TB 136. Now I'm running 136.0.1 (aarch64). So I wonder if this is something happening with 136? You probably didn't miss it, but just in case, this is happening on a MacBook Pro. I'm going to try removing and resubscribing to all of the calendars to see if that fixes it... Thanks for your help.

The Provider add-on syncs tasks and events, while the built-in CalDAV syncs events only.

To correct some issues with the 128.5.1 add-on, use the 128.5.2 version:

https://github.com/kewisch/gdata-provider/issues/891

128.5.2 now at https://addons.thunderbird.net/en-US/thunderbird/addon/provider-for-google-calendar/

Thanks so much for the advice. Based on the response, I removed the Provider from Thunderbird and then tried linking the Google calendar. Had to scramble to find the correct URL for the Google calendar, but once I did, it linked, and I got about 20 reminder notifications. I thought that was pretty good, especially when I was able to dismiss them without issues.

However, I then saw that the "today's events" pane had items from my Google calendar, but the calendar itself did not display. Shut down the program and restarted, synchronized, no improvement. Grrrr!

But after a period of computer sleep, when I brought the system back up...voila! The Google calendar was visible. If nothing else happens, it solves my problem. I don't need to see tasks, so the key piece of advice that helped was "the built-in CalDAV syncs events only." From the way the calendar install window displayed, I didn't even know about CalDAV, but removing the Provider made it obvious.

I *hope* this fixes it, but because of the history noted in my first message, I will be pretty paranoid about the Mail Provider.

Thanks again!