Widevine CDM working on new Firefox profiles but not my main one
Solution 1:
Finally solved it!
It had to do with Firefox's EME (Encrypted Media Extensions) settings, which directly relate to how Widevine operates in the browser.
The following settings were (for some reason) set to true - setting them all to false resolved the issue, and I was able to watch DRM-protected content!
So in about:config, ensure that all the following settings are set to false:
media.eme.require-app-approval
media.eme.audio.blank
media.eme.video.blank
After doing so, it was finally recognised:
