Do you have DRM allowed? Navigate to about:preferences and search for "Drm" and make sure it is enabled. If that isn't working, make sure your Wide vine is updated by going to about:addons and clicking the gear icon and selecting "check for updates"

Let me know if that helps.

Try the Firefox version from the official Mozilla server if you currently use a version from the repositories of your Linux distribution.

• https://www.mozilla.org/en-US/firefox/all/