Dashlane's site has a page for diagnosing issues with the extension, such as not being able to see the button on your Firefox toolbar: https://support.dashlane.com/hc/en-us/articles/202699011-How-to-check-your-Dashlane-extension-in-Firefox One of the answers lead to a download/install page if needed. Does that method work? By the way, if you use a lot of private browsing windows, make sure to enable extensions to work in those windows. More information on that in this article: [[Extensions in Private Browsing]].