Review for Provider for Google Calendar by Morgana
Rated 4 out of 5 stars
You have delete your Google calendar from Thunderbird and then reinstall it. See:
https://groups.google.com/forum/#!topic/provider-for-google-calendar/nSqra_q-zQ4
Probably a good idea to include information of this sort when releasing an update that requires user action.
To create your own collections, you must have a Mozilla Add-ons account.