Sorry, the Add-ons team is working on a fix for this. It looks like a certificate used to sign many popular add-ons expired. The verification process checks that certificate, and if it doesn't pass, it's blocked.

I don't know how soon re-signed versions of those add-ons will become available, or whether another workaround will be discovered. We are all hoping to learn more soon.

Ah - thank you. Is there anywhere I can stay up to date on this?

See:

• https://discourse.mozilla.org/t/certificate-issue-causing-add-ons-to-be-disabled-or-fail-to-install/39047

At about 6:10 PST we received a report that a certificate issue for Firefox is causing add-ons to stop working and add-on installs to fail.
Our team is actively working on a fix. We will update as soon as we have more information.

• Bug 1548973 - (armagadd-on-2.0) All extensions disabled due to expiration of intermediate signing cert

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Mozilla has rolled-out a fix for this. The fix will be automatically applied in the background within the next few hours, you don’t need to take active steps.

In order to be able to provide this fix on short notice, they are using the Studies system. You can check if you have studies enabled

1. Go to [=] > Options > Privacy & Security.
2. Make sure Allow Firefox to install and run studies is check marked.

I you had it disabled, you can disable studies again after your add-ons have been re-enabled.

They are working on a general fix that doesn't need to rely on this and will keep you updated.

See also:

• https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/