Update late 2019 05 04
Here is Mozillas official statement on the addons glitch:
Click here to download the statement in PDF format if you don't wish to go to Mozillas website:
2019 05 04
Today we were greated with Firefox have disabled all our addons.
No matter what you do to update or re-install your addons will solve the bug, or glitch. It's a code build error in Firefox.
If we do a simple Google search we find that this news have been covered by many sites.

Most of them do not offer a solution or work-around. And some even suggest installing Firefox nighly builds, which is totally unneccesary.
Here is how you enable your addons temporarily until Mozilla fixes Firefox:
Type this into your Firefox address bar:
about:addons
... and press Enter.
Now you will see a list of disabled addons:

Here I am showing just one of the addons disabled. But before I started ALL my addons were disabled, or restricted as Firefox calls it.
Now type this into your Firefox address bar:
about:debugging
... and press Enter.
Now you will se something like this, but without the addons enabled:

Click the circled button:
Load Temporary Add-on
Now navigate to:
user\AppData\Roaming\Mozilla\Profiles\your_profile.default\extensions\

Now select the first XPI addon in curly brackets, and click open.
You have to do this for every addon that you wish to re-enable.
The ones that looks like a email address is usually the confirm page you normally get once you installed a addon. You can if you wish to go trough these. Some addons even require you to select them.
That's it!
Now enjoy your ordinary Firefox until Mozilla fixes this glitch/bug. =)
/Kim H. aka KaxLon.