Try deleting/removing the Provider add-on then installing it afresh.

I know there is a version of Provider, and there really has to be, as this is a mainstream version of Thunderbird. If you had been using a pre release beta version then yes you could expect trouble.

I beta tested this version and it had the proper version of Provider at that time. I always check it against a Google calendar.

But, wait. Is iCal a Google calendar? I think not. "iCalendar" is one of the built in protocols and you shouldn't need Provider.

Thanks Zenos. Ical is not a google calendar, but everything I've read says i need Provider to bridge between Ical and TB. Is there a way to directly link? I tried creating a new calendar in TB ICal format, but it requires an address and ICal only gives https://www.icloud.com/#calendar. When I put that in, the calendar is empty. It's not accessing my Ical without sign in. Do you know how I can directly link Ical to TB? The only way I've seen is Provider. Error on Provider is the following:

Provider for Google Calendar 3.3 Requires Restart

by Philipp Kewisch

Allows bidirectional access to Google Calendar

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