Enable supported protected playback in desktop Firefox
Check Firefox’s DRM playback setting and its Widevine module if only protected videos fail in a service that supports Firefox.
IPTVBlogs editorial desk · 
Compare an ordinary video with a protected title
Try a video you are authorised to watch and a public sample that plays in desktop Firefox. If the sample plays while a supported subscription service reports a protection error, open Firefox Settings and look in General for DRM-controlled content. Mozilla documents a checkbox to enable it. Change this preference only when you want Firefox to play protected media.
Let Firefox handle the module
Firefox uses the Google Widevine content decryption module on supported desktop platforms. Use Firefox’s documented settings and update route. Do not install a codec or DRM extension from a pop-up. If the module is enabled and only one service still fails, note the exact Firefox version, operating system and visible error. Use the service’s supported browser list to check whether its protection requirements differ.