Accepting invite does not create an calendar entry in iCloud

Hello

I have several e-mail accounts and a iCloud account for my calendar and contacts. This is working well, but when i click to accept an invitation that was sent by mail. It adds the calendar entry to the local calendar, and not to my calendar on iCloud.

I do not found any setup to config it correctly. In Thunderbird there i was asking in whitch calendar i would like to add.

May somebody has me a hint, to solve my problem.

Thx Gregor