None of my add ons show anywhere, can't unistall or change settings, clicking on add ons brings up a blank page
Nothing at all when I go to add-ons. I can not delete or disable any since I can not see them. One of the add-ons has a bunch of settings but I can not change them. When I open Add-ons manager there is nothing, not under any of the categories on the left. Extensions, Plug-Ins, Appearance, Gett Add-ons, all blank.
If you see disabled, not compatible, extensions in "Tools > Add-ons > Extensions" then click the Tools button at the left side of the Search Bar (or click the "Find Updates" button in older Firefox versions) to check if there is a compatibility update available.
If this hasn't helped then also try to delete the addons.sqlite file.