my Llightning calendar has disappeared.

What is the status of Lightning in your Add-Ons Manager? Please post a screenshot with the entry for Lightning visible. http://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

I've tried installing the .xpi file using Firebird and Chrome.

Lightning is an extension for Thunderbird. I cannot follow your logic.

I installed 7zip to open .xpi files but still won't work.

What did you expect to happen? A miracle?

https://addons.mozilla.org/en-US/thunderbird/addon/lightning/

If you click on download it gives you instructions on how to install a Extension in Thunderbird.

How to Install in Thunderbird Download and save the file to your hard disk. In Mozilla Thunderbird, open Add-ons from the Tools menu. From the options button next to the add-on search field, select "Install Add-on From File..." and locate the downloaded add-on.

thought this worked but not sure now. I did the add-on download after finding the settings/install from file options (missing in most instructions).

Got msg that Lightning would be installed after restarted - so far, so good but after restarting I can't find Lightning / calendar tab or option anywere on Thunderbird screen.

Any ideas where I can dig Lightning out and actually see it?

thaks

I got banner stating Lightning would be installed after restarting Thunderbird which I did, I also restarted computer but the calendar tab/option doesn't show up.

Any help on actually getting Lightning to show up?

thanks