hi, this is/was caused by an unforeseen technical problem unfortunately (an expired certificate used in the process of verifying addon signatures).

a fix for this is already being rolled out - for details, please see: Add-ons disabled or fail to install on Firefox

How much longer will it take to restore the extensions? Why was the update or change tested before implementation?

assuming you're on the esr channel (your system details show that you are using firefox 60), an update to 60.6.2esr rectifying the situation should be released later today.

the part that broke wasn't caused by an update or change btw - it was a part of the signature verification mechanism for addons that was already shipping with firefox for years.

Mendel1980 said

There was a Bug-A-Boo with a Certificate Expiration Date dealing with the Add-ons. There's a new FF Version with the main Fix, 66.0.4.

Mozilla Blog Post Update:
A Firefox release has been pushed — version 66.0.4 on Desktop and Android, and version 60.6.2 for ESR. This release repairs the certificate chain to re-enable web extensions, themes, search engines, and language packs that had been disabled (Bug 1549061).
There are remaining issues that we are actively working to resolve, but we wanted to get this fix out before Monday to lessen the impact of disabled add-ons before the start of the week. More information about the remaining issues can be found by clicking on the links to the release notes above.
(May 5, 16:25 EDT)

~Pj