All themes (default, dark, etc) are disabled and can't be enabled after unexpected system restart
After unexpected system restart, Firefox reverted to the default/no theme, clicking "enable" for any of the other themes does nothing, the remain "disabled".
See screenshot.
Firefox 69.0
Wšykne wótegrona (2)
On Friday, May 3rd, 2019, we became aware of an issue with Firefox that prevented existing and new add-ons from running or being installed. We are very sorry for the inconvenience caused to people who use Firefox.
Mozilla has released updates to resolve the issue. See the article Add-ons disabled or fail to install on Firefox and this Mozilla Blog post for more information.
Pulkit Krishna said
On Friday, May 3rd, 2019, we became aware of an issue with Firefox that prevented existing and new add-ons from running or being installed. We are very sorry for the inconvenience caused to people who use Firefox. Mozilla has released updates to resolve the issue. See the article Add-ons disabled or fail to install on Firefox and this Mozilla Blog post for more information.
I'm aware of the certificate from May, this is not the case however: All other addons work, only the themes are not. As mentioned, I'm using the latest, version 69.0