Hi.

It is a bit hard to know exactly what has happen for you, if you com back with more info (firefox version and Link Password version) we give you more help.

My guss is you have upgrade the addons or Firefox, since Firefox version 57 I have rewrite the addons and some functionality has be moved to new locations (see screenshots).
If you running a older version of Firefox (before 57) please install version "Version 4.0.1.0.1-signed.1-signed"