Hi Zoli, please ignore the fake support email address someone is spamming here. A genuine community support volunteer will reply in your thread on this site (https://support.mozilla.org/questions/1289069)

Do you have the Widevine plugin installed (Add-ons -> Plugins) that is required for playing DRM protected content ?

Try to toggle DRM off/on to see if that makes Firefox (re)load DRM components.

• Options/Preferences -> General: Play DRM
• https://support.mozilla.org/en-US/kb/enable-drm

You can 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/#product-desktop-release