You can check for problems with the extensions registry files in the profile folder. Try to to reset the extensions registry and rename extensions.json (extensionsOLD.json) and rename/remove previously used extensions files like extensions.ini and extensions.sqlite when present and rename/remove compatibility.ini in the Firefox profile folder with Firefox closed. *https://support.mozilla.org/en-US!:[]/kb/Profiles New files will be created when required. See "corrupt extension files": *https://support.mozilla.org/en-US!:[]/kb/unable-install-add-ons-extensions-or-themes You can check for possible updates in case of issues. *click the cogwheel button (left of the Search bar) on the about:addons page to "Check for updates" You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page. *Help -> Troubleshooting Information -> Profile Folder/Directory:<br>Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder *https://support.mozilla.org/en-US!:[]/kb/profiles-where-firefox-stores-user-data Note that some extensions may not work in Private Browsing mode. *https://support.mozilla.org/en-US!:[]/kb/extensionss-private-browsing