1) ContextSearch web-ext https://addons.mozilla.org/ru/firefox/addon/contextsearch-web-ext/ Can't add Search Engines Add button does nothing. Import One-Click Search Engines from search.json.mozlz4 never ends, just shows spinner and it rotates forever Import settings from other browser does not change any setting. 2) Yandex Visual Bookmarks https://addons.mozilla.org/ru/firefox/addon/yandex-visual-bookmarks/ Just blank page instead of bookmarks 3) Stylish https://addons.mozilla.org/ru/firefox/addon/stylish/ Try to add new style. Can write it down but save button does nothing. 4) Tree Style Tab https://addons.mozilla.org/ru/firefox/addon/tree-style-tab/ Theme settings do not change bars appearance. As I have all these problems simultaneously and all these add-ons work fine on other PC I guess the installation is broken. Something with add-ons setings or something.