Things have changed with V91. Quite radically really. Leave the URL blank and enter your gmail email address and click find calendars. You will be prompted for an oAuth password if you are not already using oauth to access that mail account and then your available calendars will be listed for you to select.

Use the following url https://apidata.googleusercontent.com/caldav/v2/calid/user and replace calid with your gmail address, or simply do as Matt says.

Use the following url https://apidata.googleusercontent.com/caldav/v2/calid/user and replace calid with your gmail address, or simply do as Matt says.

That is for V78. 91 fails on google if you enter a URL at all. It is designed to get the calendars via discovery

Stans said

Use the following url https://apidata.googleusercontent.com/caldav/v2/calid/user and replace calid with your gmail address, or simply do as Matt says.

That is for V78. 91 fails on google if you enter a URL at all. It is designed to get the calendars via discovery

It worked just fine for me on TB 91.0.3, four times ( two different accounts on two different profiles), just before I replied here.

Thanks for your answer, @Matt.

Leave the URL blank and enter your gmail email address and click find calendars.

I don't quite understand: as you can see in the screenshot, there's no place to enter an email address – only a username and a location. Entering the URL (either in full or just the email-address-like part) in either yields the same results.

Also, in case it matters, please note that I don't have an email address for this calendar: it belongs to a group, and the address is of the form <many letters and digits>@group.calendar.google.com. But I'll be happy to try and enter this instead of the URL if only I could find where to do so.

email address and user name are the same thing for google.

Thanks for your answers, @Stans.

Use the following url https://apidata.googleusercontent.com/caldav/v2/calid/user and replace calid with your gmail address

Just to make sure I understand: do you mean I should write "user" instead of "events" at the end of the URL, or is there any other difference? If that's the whole thing, then I had already tried that and it didn't work either (sorry I forgot to mention it in the original post). If there's any other difference, please explain it explicitly.

Also, in case it matters, please note that my calendar ID is not a gmail address, but of the form <many letters and digits>@group.calendar.google.com – I don't think that should matter, but maybe it does?

Thanks, @Matt.

email address and user name are the same thing for google.

Well, as I said above, I tried that too, and got the exact same result. The spinner just keeps spinning, and I'm never asked to sign in / authenticate.

goto the google web for your calendars and attach the group calendar to your account, just as you would a public holiday calendar, then it will appear as a calendar for your personal email address when you enter it as a username.

@Tom just a thought.... these calendars require oAuth authentication, which requires cookies to be enabled in Thunderbird. If you or some security software has disabled them then authorization can not occur and everything fails. (endless circling)

Otherwise have a look at the thread I linked to below. It covers the subscription process in google as well as the Thunderbird one.

@Stans Please see my discussion here https://thunderbird.topicbox.com/groups/daily/T98007421760a2189-M7c21cd08849ba3840af2c828/psa-changes-to-google-authentication I was slow to learn, but John and Geoff did get me sorted eventually.

I tried the URL and it did not work. My experience was much as described by Tom.

Thanks for your answers, @Matt; unfortunately, this still isn't working: it doesn't matter what I type in as username and/or location, I'm never redirected to log in / authenticate. Cookies are enabled (see screenshot taken from settings page). Any ideas what else could prevent me from being redirected to authentication and how to resolve that?

The CalDAV URL that works for me is:

https://apidata.googleusercontent.com/caldav/v2/myname@gmail.com/events

Works properly in a new 91 profile with no accounts, by entering the URL in the Location box.

Thanks, @sfhowes. Can you please explain how this URL is different to the one I've been trying to use? Is it the fact that it's `@gmail.com` as opposed to my group calendar which is `@group.calendar.google.com`? Should that make a difference? Notice that the calendar I'm trying to use is a group calendar and not my private calendar from my own email address, and that this is what its ID looks like.

Regardless, the problem is I'm never redirected to authenticate, no matter what I put in username and/or location (including trying with my own email address instead of the group calendar ID); I have no reason to believe the problem lies within the URL (which might or might nor prove problematic once I get Thunderbird to allow me to authenticate and actually try and retrieve my calendar).

Delete any saved Google password stored in Thunderbird's password vault and restart Tbird. If the Google authentication page still doesn't open, delete Tbird's cookies and restart it then try again.

I had to delete the password (oauth token) stored for my Google calendars when I upgraded to 91. They had been added before and weren't synching/enabled anymore. Re-enabling them wasn't heading anywhere as it kept re-prompting for a password. I unsubscribed from them and deleted their stored tokens. Only then did it load the Google oauth page when discovering the calendars.

I haven't tried adding a group calendar, but accessing it might require some extra steps:

https://support.google.com/calendar/answer/37648?hl=en#zippy=%2Cpublic-address%2Csecret-address

https://support.google.com/a/answer/1626902?hl=en

Setting the correct permissions might be related to the password problem, but it's still worth following the steps to delete and re-enter the password in the OAuth window.