Rated 5 out of 5 stars

Danke @pemue88 für den Hinweis. Ergänzend noch die Info: Wenn man eine andere als eine Gmail-Adresse für sein Google-Konto nutzt, muss man bei Adresse "google.com" eingeben.

And now for everybody who doesn't understand German:

Thunderbird 141 supports Google Calendar without the add-on: Add "New Calendar" -> select "On the Network" -> enter your Gmail address as the username (leave the "Address" field blank) and click "Search Calendar." If you use an e-mail address other than gmail you need to enter "google.com" in the address field.

Danke Philipp Kewisch für deine Arbeit!

Rated 5 out of 5 stars

I reinstalled both Thunderbird and the plugin. Working well again now.

This review is for a previous version of the add-on (128.5.2). 

Rated 3 out of 5 stars

"After the last update, when displaying the reminders window, the buttons in this window do not work, pressing the “Discard” button does nothing, if it is set to mute for x minutes, the time is not displayed either, it does not work, so every time Thunderbird is started it shows all reminders again.
Please, can you correct it?"
Same here

This review is for a previous version of the add-on (128.5.2).