Do your calendars have an associated email account defined in Properties?

https://superuser.com/questions/489189/accept-and-decline-button-missing-in-thunderbird-when-receiving-an-invitation

Thanks for the response and the help! However all my calendars have an associated email address and I tried all the possible solutions from your link. Sadly none of them worked.

I even tried deleting all of my email accounts and calendars and then setting up one email account with only one calendar associated to it. But it didn't work.

Furthermore, I checked the config editor but I couldn't find anything strange there.

I sent an invitation from outlook.com to a mail account in TB that has a local calendar associated with the same mail account (78.5.1/W10). The Accept/Decline buttons appear (see picture). The buttons also appear if I send to an account that is not associated with any calendar. What kind of calendar do you have in TB, and where does the invitation come from?

Thanks for the effort. I also got invitations from outlook. I have a caldav calendar from my owncloud server.

I did reset Thunderbird and set up my email account and calendar again and now the buttons are back. Therefore I will just reconfigure everything manually and then it should work again.

Hello, I have the same problem, on Windows using Thunderbird 78.8.1, the control panel "invitation to an event" doesn't appear. on Ubuntu, using the same acount email, it work.

I tried on an other Windows computer with a fresh install of Thunderbird, same problem.

Thanks