Update: It appears Firefox 66.0.4 has resolved the issue. Chances are you have never experienced this problem.
On 4 May 2019, one of the Mozilla digital certificates used to sign Firefox add-ons expired. With this certificate no longer able to verify the authenticity of the add-ons, user across the faced the loss of access to their Firefox add-ons.
This post teaches you how to recover from this failure in about 15 minutes and resume your daily routine work as if this has never happened.Read the rest of this entry