This will disable add-on signature enforcement; Enter about:config into your Firefox address bar Click the I'll be careful button Find xpinstall.signatures.required in the list Right click the preference Select Toggle until the value is false https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox

https://wiki.mozilla.org/Firefox/AddOns/Status/Updates#Exec_Summary “Currently targeting Signing with no pref to turn off in Firefox 47”

I followed this instruction exactly, "Find xpinstall.signatures.required in the list Right click the preference Select Toggle until the value is false"

I did not understand material in blue that followed. Thanks for input FredMcD. Hope this solves the problem.

It is possible that there is a problem with files in the profile folder that store the extensions registry.

Delete the extensions.* files (e.g. extensions.json, extensions.ini, extensions.sqlite) and compatibility.ini in the Firefox profile folder to reset the extensions registry.

• https://support.mozilla.org/kb/Profiles

New files will be created when required.

See "Corrupt extension files":

• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions
• https://support.mozilla.org/kb/Unable+to+install+add-ons

If you see disabled or not compatible extensions in ""3-bar" menu button/Tools > Add-ons > Extensions" then click the Tools button at the left end of the Search bar to check if there is a compatibility update available.

If this didn't help then delete addons.json and possibly prefs.js in case there is a problem with preferences.

There is software like Advanced SystemCare with its Surfing Protection feature that can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

As a general comment, where extensions are not signed, there are often acceptable alternatives if you work through the Firefox list of available Add-ons(sometimes the alternatives are even better).

The solution suggested by FredMcD did not work when the computer is turned off, and then restarted, the extensions are removed.

The solutions suggested by other people I did not try because they are beyond my ability to carry out. I wish I had never upgraded to the latest Firefox, 43.4.

If anyone has a copy of the Firefox 42, or older, please send it to gypsywolf@mail.com and I will remove 43 and go back to 42 which worked. If I dont receive a older Firefox I will try a different browser.

Type about:support in the address bar and press enter.

Under the page logo on the left side you will see Application Basics. Under this find Profile Folder. To it’s right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Delete the extensions.json, extensions.ini, extensions.sqlite and compatibility.ini files. Restart Firefox.

Appreciate all your efforts FredMcD, removed the 4 files saved, and turned off computer, Addons are still missing when I returned, However, I am going to try it again in case I missed a step.

Just reload the add-on from it's web page.

I did try loading the addons individually, from their original location, but that did not work, however, a few of the addons are present and appear opposite the search line at upper right, but none of them ever appear where it use to show your addons at the side. In fact, it says I do not have addons of this type there. I also deleted and reinstalled Firefox but that did not work either.

Thanks for everyone's suggestions and help, I will wait for the next update and try again at that time.

I went gone over all the steps suggested in solutions above and found this fact:

The first time I tried the solution of removing the four files from the profile I removed all four, however, when I tried it again, the file "extensions.sqlite" never appeared again, so it was only deleted once and never reappeared.

I also tried the program FEBE which restores all windows settings and your addons if you lose them or have a problem. This helps to restore Firefox quickly even though the addons are still removed when you turn off the computer.

Even though the addons are removed from the usual location, the key ones are still present and appear to the right of the search line at the top of the page.

Although the solution I was seeking as not happened, I consider the case closed because I have the addons in a different location for use.

extensions.sqlite was used in previous Firefox versions and is no longer being used (replaced by extensions.json).