Thunderbird needs to login google every time (CalDAV) Befor: I use Thunderbird/Lightning for my mails and for my calendar. This issue is about the calendar. I'm a google-user. 

A short while ago I started to change from "Provider for Google's calendar" to the CalDAV way because I couldn't import invitations to my calendar. So far so good. 

But now, every time I start Thunderbird or the calendar would like to synchronize it pops up the following window (for every calendar. I have 5!):



I could not find any preferences where I can say that Lightning can use it every time.

So, am I blind or how can I fix this?
I also had this problem, and just fixed it. For me, the problem was that I recently changed my Google password, and I think Lightning was still using the old one. In the pop-up window that ask you to click Accept, in the top right, you can see the name of the Google account, click there and there is an option to log out. Then try again.

I have also read on a different thread that the problem can also be caused if you try to login with the Google account - again, use the link in the top right corner to check that Lightning is using the correct Google account.

Hope this helps