"Browsing Protection by F-Secure could not be verified for use in Firefox and has been disabled". This notice appeared on May 4, 2019
There is another discussion about trouble:
Sounds that it is not pinned to F-Secure side; but rather to Firefox infrastructure.
Are you talking of https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/ ?