Extensions do not work on Mozilla websites because content scripts are blocked on several restricted domains that have special powers to access and modify personal data.

• https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Content_scripts

Hi, according to the permissions list, the extension should be able to interact immediately with the page content on these 5 sites:

Access your data for sites in the nflxso.net domain Access your data for sites in the nflxvideo.net domain Access your data for sites in the netflix.com domain Access your data for sites in the youtube.com domain Access your data for sites in the lingq.com domain

The message would be normal for all other sites where it doesn't already have permission to interact with the page content. But the information in the message might be incomplete. The extension also has the "activeTab" permission, so you might only need to click the button to grant permission on other sites, "on demand." It really depends on how the add-on is designed.

If you can't get it working where you need it, I noticed LingQ has a support forum. There are some Firefox posts already (https://forum.lingq.com/search?q=firefox), but probably it makes sense to start a new thread.