Open the Add-ons Manager and locate the entry for Lightning. Create a screenshot and attach it to your reply. http://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

I have added two screen shots. I am not sure which you were referring to. Thanks.

I think we expected to see a view like this (below) which tells us if Lightning is installed, or indeed, if not. Or maybe installed but disabled.

Your first picture tells us that it isn't installed.

Can you tell us in more detail what does happen; telling us "nothing works" doesn't tell us very much at all.

I have added the screen shot you were looking for.

Thursday morning I started my laptop to check my emails. Thunderbird opened with no problems. With it my task reminder list came up as well. I didn't have time to attend to any of the tasks so I snoozed some and just left the others. After I was done answering emails I shut both the programs and my laptop down for the day.

When I came home that evening I started both my laptop and Thunderbird up. I answered emails and then realized that my task reminder list did not come up. When I went to look at my calendar it was not there. Just the email program was open. I have sent you a screen shot of the program as well.

I thought maybe it had somehow gotten disabled so I searched Add-on, Extensions and Plugins. It was not listed. I then went to the Program Files (x86), then to Mozilla Thunderbird Folders to see if there was anything there, but couldn't find anything. I was hoping I would at least find my files. I looked in the Mozilla Maintenance Service and Mozilla Firefox folders as well just in case it was in there. There was no Mozilla Lightning Folder. It looks like it was never installed. I can't even find it in my Download Folder. I have sent you both of these screen shots as well.

I know it was installed becasue I have been using it for months. I never questioned its stability and transferred all my appointments, tasks and reminders from my old calendar and now all that info is gone.

I read the blog and thought maybe an update to Thunderbird was done, but I can't remember there being one. But I thought if I tried to update or install the calendar again I could get my info back, but that didn't work.

I am very careful with my laptop and what I download becasue I rely on it for my business. Also I am the only one who has access to it.

I hope all this helps.

You'll need to install Lightning again. Apparently you already downloaded the current version 4.0.2.1.

Regardless of what has been in the past, it is at present not installed.

So, what happens if you go back to the position shown in your first picture and click on "Add to Thunderbird"?

When I try to install Lightning from my download folder I get a little pop up that tells me that it is not compatible with Thunderbird 4.0.2.1. I know that I have 3.8 and have not tried to upgrade it because I did not want to make this any worse.

When I click the Add to Thunderbird button nothing happens. I have already tried it several times even shutting down Thunderbird after clicking the button. I also tried restarting my computer. It will not add on.

I would rather not update my Thunderbird unless you feel I will get back all my calendar info. Also can you guarantee that I won't loose all my emails in the process? I am afraid of adding more pain to this "headache" I already have.

By the way...Thank you so much for you help...

Hang on. You have mentioned "Thunderbird 38.2" and now you talk about "Thunderbird 4.0.2.1" and you say "I have 3.8".

You need to be precise.

In Thunderbird, Help|Troubleshooting Information will tell you a version number. Mine says "38.2.0" and since this is the current formal release of Thunderbird, you will get the corresponding Lightning 4.0.2.1 from the Lightning page.

And I can't see a version 3.8 in the repository of past releases of Thunderbird.

Now you have raised the issue of your choosing not to update Thunderbird, I feel we need to know exactly which version you do have. If it isn't 38.2.0 then we need to find you the appropriate version of Lightning.

I have sent you a screen shot of the version I have.

I miss typed what version I have.

I see now what some of the confusion is. When I try to install Lightning from the Download folder I am unable to because I get a pop up window that says Lightning cannot be installed becasue it is not compatible with FIREFOX 40.0.3 My apologies, I thought it read Thunderbird, not Firefox. I have sent that screenshot as well.

That's a common problem, and it happens because both Thunderbird and Firefox use xpi files for add-ons, and if you download a Thunderbird add-on in Firefox, Firefox will assume it's a Firefox add-on.

Here is a link to my website's article on how to download and install add-ons. I doubt that the regular download-and-install method is going to work for you, as you have already been into the "get add-ons" page and clicked the appropriate "Add to Thunderbird" button.

I give you two other ways to use the file you have already downloaded. Try either, or both, of them. To be explicit, you can drag-and-drop the xpi file onto the add-ons page, or you can navigate to your downloaded file from the button next to the search box on Thunderbird's add-ons page.

It's back!!! All of it. I opened my email to see if I had anything from you and it was all back! Thank God!! And thank you too for all your help.

I do have one more question... How the heck to I bad this baby up so I don't loose anything again!!!?

I mean BACK this baby up...:)

Backup the entire Thunderbird profile. See http://kb.mozillazine.org/Thunderbird_:_FAQs_:_Backing_Up_and_Restoring

I still wish I knew what happened to avoid it again and maybe help someone else in the future. I'm just glad it all came back. I guess if anyone reads this in the future I would tell them to try everything I did and then wait a day or two... Thank you so much for your help.