Make sure your Google Calendar is not read-only. Right-click the calendar - Properties to check.

The calendar was checked "read-only" so I unchecked it. I could dismiss one item, but it automatically went back to "read-only" and no others could be dismissed again. Thoughts?

Try to delete the Google Calendar in Lightning and restart Thunderbird. Then re-create the calendar. Since it's a network calendar no data will be lost.

I appreciate your help, but this didn't work either. I tried this two different times, and both failed. It keep resetting my Google calendar to "read-only." Any other thoughts?

I tried this two different times, and both failed.

This isn't really a useful statement.

What exactly did you do?

What happened?

OK, I unchecked "read-only" from the calendar properties, then tried to dismiss. It seemed to work until I got the return "An error has occurred" The Error code was "modification_failed". The property is then reset to "read-only".

I continue to be unable to dismiss or snooze any calendar reminders. I have also deleted the calendar and recreate it, but it always is created as "read-only" and I continue having the problem as described above.

How do you access your Google Calendar, via the Provider extension or CalDAV?

I guess it is the Provider extension. It is a private calendar via ICAL url.

Guessing doesn't help. With the latest version of the provider extension you only need to provide your user ID and password. You don't have to look up a URL anymore.

Make sure you do have the latest version. https://addons.mozilla.org/en-US/thunderbird/addon/provider-for-google-calendar/

FANTASTIC! This solved my problem. This needs to be highlighted in Thunderbird instructions. I followed what I found on the forum, but it obviously didn't apply to the latest version. THANK YOU!!