What is the status of Lightning in the Add-ons Manager? Lightning is the Thunderbird calendar add-on. You may want to provide a screenshot with Lightning visible. http://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

Thanks for getting back to me. Lightening doesn't show in the Add-ons manager, and neither could I install (either on-line or from a file) and enable it. It was only after reverting from the new 38.3 back to 38.2 that it appeared again with no extra action. From memory I believe that v38 was the first Thunderbird release that incorporated Lightning functionality without requiring it to be installed as an additional add-on for first time users. It is as though something in the 38.3 upgrade hasn't taken account of something from that earlier release design decision.

At the moment I am back working hapilly on 38.2 and will stick with that unless I hear that the upgrade fault has been fixed.

Thanks.

There isn't really an upgrade fault. And Lightning is still an add-on. I had some problems upgrading Lightning as well, and I believe it is caused by anti-virus software. You can try to disable your anti-virus real-time scanner and install Lightning again.

Hi, thanks for trying to help but as a software tester of 30+ years it sure seems a bug to me. When something works before an ugrade, doesn't work after an upgrade, then works again when you back out the upgrade that pretty well points to the upgrade as the root of the problem. I only posted it here as an aid to developers because when I tried to follow any links to report a bug this is where they took me. It's up to whoever maintains the product to take notice or not.

Just to pick up your points though, the anti virus on or off made no difference at all and regarding the status of lightning as an add-in, there is no sign of it or any reference to lightning/calendars/tasks etc in any of the product menus after upgrading to 38.3 so I can't do anything. All the uual references to lightning in menus etc. return as soon as I back out and revert to 38.2.

You can still install Lightning just as every other extension in case it's gone with 38.3.0 (for whatever reason). https://addons.mozilla.org/en-US/thunderbird/addon/lightning/

There are a couple known issues though: 38.3.1 bug 1211160 calendar 4.0.3.1 is a workaround for 38.3.0 — Thunderbird Version 38.3 Buttons not working menu items // bug 1211291 – Folders are visible, but messages are not.

bug 1182629 – update to 38.1.0 from 38.0.1 re-enables disabled Lightning