If you accidentally shared your calendar's Secret address, click Reset to create a new Secret address. Do not share this address with other people.

Important: Only you should know the Secret address for your calendar. Paste the link as directed by your other calendar application.In the 'Secret address in iCal format' section, copy the link.On the left panel, under “Settings for my calendars,” click the name of the calendar you want to use.In the top right, click Settings Settings.On your computer, open Google Calendar.My Thunderbird is the latest Beta 24.0.If your calendar application doesn't have a full sync option, or if you want a read-only view of one calendar, you can sync your calendar to the application using a link to iCal. I had Lightning 2.6b2 but just today I upgraded Lightning to version 2.6, yet that did not fix the issue. If I just try switching on the calendar (by right-clicking on one of them, selecting properties, checking the box for 'Switch this calendar on') then the calendar turns on for a fraction of a second and then becomes disabled again.

To fix that, I have to restart Thunderbird. This worked for me as well, initially, but I've noticed that both of my Google calendars become disabled and have that 'Google Calendar momentarily not available' message with the yellow triangle/exclamation point icon if Thunderbird & Lightning are open after my PC resumes from sleep mode. I then re-enabled offline support and everything has continued to work fine. Once I disabled the offline feature, they started working again.

I was able to restore full functionality by toggling the 'Offline Support' option in the calendar properties for each calendar. Running Thunderbird Beta 24.0 and Lightning 2.6b2. Kbmcguire wrote:Had the same issue with all of my google calendars.

Thunderbird google calendar