Add your Google calendar as a CalDAV calendar from the 3-bar menu icon, New Account, Calendar, On the Network, enter your gmail address, enter your account password in the OAuth2 window, ... select the calendars.

Thanks. I assume you refer to the three bar icon on the Lightning calendar on my laptop. I followed your instructions, and in "User name" I put my Gmail address. This gives gmail.com automatically in "Location", but when I click "Find calendars", it can't discover them. Any thoughts?

Just a further point: one attempt generated a large blank screen that vertically filled my laptop. I could find no way to reduce its size, so the may have been a message at the top that I could not see.

The blank window might be the OAuth authentication dialog, which will fail if cookies aren't accepted in TB (not browser) Settings/Privacy & Security. If you have a VPN, that will also block authentication.

Thanks again. Cookies are and were accepted, and I don't use a VPN. Cheers, Colin.

The Google calendar syncs and works properly on my system. The blank window might be a profile issue, or possibly antivirus/security app interference.

Does the same thing happen in safe/troubleshoot mode (hold Shift when launching TB)?

Thanks for your patience. Using safe mode allowed me to complete the process you outlined in your first reply. Sadly, I still have not synced the calendar with my phone. My two Google accounts both appear in the phone calendar settings, and Lightning also appears on the list.

I've switched them all on on the phone, and tapped the "Sync now" button.  I've tried restarting the phone, but I still can't seem to get my Thunderbird calendar to show on the phone calendar.  Update:  For the first time in ages I've gone into Google Calendar on my laptop, and see that the problem is not with the phone, it's that Lightning has not synced with Google.  In Google, I can see the "Colin Lightning" is listed in Settings.  There are options there including a secret address in iCal format - is that something I should use?

I've no idea why there's a reference to Lightning, which was the TB calendar add-on until several years ago. It might be worth removing all Google calendars with 'Lightning' and adding them again.

If you have hardware acceleration enabled in normal mode (Settings/General), disable it and restart TB. Acceleration is disabled in safe mode, which probably explains the blank screen fix.

OK, thanks for your advice, but I seem to be going round in circles, getting nowhere. I guess I'm not up to all this, so I've decided to give up.

Perhaps I need a whole new approach. What I need is a Calendar on my laptop which will sync with my phone. Perhaps I should give up on Thunderbird, and build a new calendar on Gmail.

Cheers,

Colin.