I also have this issue. I've also discovered that I can't add a new event.

The other day, I accepted the update to version 91.0.01. I quickly discovered that my lightning calendar events were missing. My calendars were listed on the left panel with buttons that said enable. I selected them and they disappeared but nothing happened. I then did a Microsoft system rollback to my old T-Bird 78 version. Events returned but I lost my contacts and can't get them back. I downloaded the Bird from your site and reinstalled it. I still have the same issue. Can someone please help me?

re: The other day, I accepted the update to version 91.0.01.

Thunderbird is not updating from 78* to 91* If you had version 78.12.0 then a Thunderbird update would update to version 78.13.0

If you have another updater software on your computer performing the update then it would not be aware that Thunderbird is currently not auto updating. This info is available in release notes: Thunderbird 91 is only offered as direct download from thunderbird.net and not as an upgrade from Thunderbird version 78 or earlier. https://www.thunderbird.net/en-US/thunderbird/91.0.1/releasenotes/

Some people are not even aware that another program either updater software or even some Anti-Virus products have that ability to say another version is available and even force the upgrade.

I'm trying to find out whether people are getting problems because they allowed other updater software to update Thunderbird to 91.0.1 OR did people deliberately choose to uninstall 78* and then download and install 91*

I allowed the update 91.0 from Thunderbird and didn't uninstall 78* Since that update I have also allowed the update 91.0.1 thinking it may resolve the issue, but no luck!

That is exactly what happened. I used Iobit software updater.

Thanks for feedback. So basically, Thunderbird is not responsible for the update. Lobit software updater located a new version had been released - 91 - but Lobit had no knowledge that the current update offered by Thunderbird was from 78.12.0 update to 78.13.0 and not 91. So it went ahead and installed 91

Not sure what you are currently using, but Install version 91.0.1

There are many users reporting the calendar is missing after the update. If you were using the Provider add-on, disable or remove it, then add the calendar directly as a CalDAV calendar:

https://support.mozilla.org/en-US/questions/1304356#answer-1368791

https://github.com/kewisch/gdata-provider/issues/194

Well, I downloaded 91 from Thunderbird.net, not any other provider and it happened.

My solution was to reinstall 78 to another directory, retrieve the profile form backup to another dir.

Point TB 78 to the new location, export the calendar and then import it to 91.

Workaround, not a solution.

This wording

"Thunderbird 91 is only offered as direct download from thunderbird.net and not as an upgrade from Thunderbird version 78 or earlier.

Does not state or imply any incompatibility, just that it's not freely available yet and is not an automatic upgrade.

I have never uninstalled old versions, should not be necessary with properly written software.

Richard

Release notes say: "Thunderbird 91 is only offered as direct download from thunderbird.net and not as an upgrade from Thunderbird version 78 or earlier.

re quote Does not state or imply any incompatibility, just that it's not freely available yet and is not an automatic upgrade.

Thundrebird 91* is freely available that's why it's released. Any person who never used Thunderbird before can download and use it. Or indeed anyone can choose to download and use it. But as with the upgrade from 68* to 78* there were major changes and hence the same ocurred - auto update from one series to the next was delayed. There is a major upgrade from 78* to 91* and it is expected there maybe a few gremlins to sort out as can occur with a major change, so Thunderbird is currently not auto updating from 78.12.0 to 91* at the moment.

This calendar issue reported is occurring with people who used software to update or who manually updated to 91* and the developers are aware of it.

You can read the number of new things and changes just in that initial version of 91 https://www.thunderbird.net/en-US/thunderbird/91.0/releasenotes/

If you see a new release is offered and the Release notes say auto updates are not currently being offered then you can assume there are major changes. Whether you choose to go ahead and update is up to you.

Thunderbird is allowing some time to get feedback on issues which they were not ware of at time of release so they can get them fixed prior to offering an auto update to the majority of users currently running a 78* version.

If you have Thunderbird controlling the updates then it did offer an auto update from 78.12.0 to 78.13.0

If you have another updater software which is controlling all your updates then that product would not be aware of the update from 78.12.0 to 78.13.0, so the update would be to 91*

So the auto update you would get depends upon whether Thunderbird was in control of auto updates.

If you were prompted about an update, but you normally choose to go directly to the official webpage and download and install latest version directly, then you would have only seen the 91* version, so it's not unreasonabe you would have thought well that's the update. In these situations you should always read the release notes so you are better informed. The following link is where current main release in all languages is available and there is a 'Release Notes' link near the top.

• https://www.thunderbird.net/en-US/thunderbird/all/

I advise you always read the 'Release Notes' as it may provide you with more information on whether to proceed at that time. This is a link to where you can access the 'Release Notes' for any released version:

• https://www.thunderbird.net/en-US/thunderbird/releases/

If you have been updated to 91* then any further updates will be in the 91 series. As I'm typing this the current is 91.0.3 It is advised you allow those updates.

Advice: Understand what program you are allowing to control the updates for programs on your computer. If you have anything like eg: Lobit software updater performing updates then see if it offers a list of programs that it checks and remove Thunderbird.

I would strongly advise that you ensure Thunderbird is in control of updates. Check settings within Thunderbird.... Menu app icon > Options/Preferences > General scroll down to 'Updates' section Uncheck the checkbox - do not select this: 'Use a background service to install updates'

Ideally, create a backup before updating especially if updating to a major new release and even more so if Thunderbird are stating they are currently not offering it as an 'update'.

Many thanks to Rich-J for providing a workaround.