please try to uninstall first then install it again,and even after that u again getting same message then tell us.we will tell you other options.

I have tried that several times will not launch

You can switch to one of the other tabs if the Get Add-ons tab isn't working on the about:addons page.

Do you have a lot of extensions installed?

By default the "Get Add-ons" tab is selected if you open the about:addons page (Firefox/Tools > Add-ons).
The "Get Add-ons" tab on the about:addons page loads content from the Mozilla server and that can take some time especially if you have a lot of extensions installed or the server is busy.
Firefox sends a list of installed extensions to the server to prevent extensions that you have install from appearing in the list that is displayed.
You can click on the Extensions tab to see the installed extensions or one of the other tabs to see other installed add-ons.

You can visit the Add-ons website directly and search for extension.

• https://addons.mozilla.org/firefox/