Hello Everyone I'm having troubles with playing some Youtube-Videos and Twitter Videos. I had to re-install my Windows 10 (64 Bit) due to some hardware-issues which are not related, and I'm having this issue since then. Here are the steps that I already did: -Removing all Add-Ons -Starting in Safe mode - Deinstalling and reinstalling Firefox, then starting in safe Mode -Deinstalling Firefox with a tool that also deletes all Firefox-Related Registry Keys and App-Data Files and reinstalling it to a different path (other HD) -Disabling add-ons - Disabling Open264 Videocodec and widevine content decryption module (more just because of frustration^^, but I was then able to play some Youtube videos after this one) - mediasource.enabled is active (and all the other ones as well) -Installed addons (even though it didn't work with them disabled as well): NOscript( youtube videos are allowed, some of the are working), Ublock Origin, Video Download Helper, HTTPS Everyhwere, Tree Style Tab, Limit distracting sites - Updating to the newest Firefox-Version (which came out today) Btw: on https://www.youtube.com/html5/ it tells me that everything works fine and I have of course the newest Firefox-Version installed. Do you guys may have any other ideas? Thank you for your help. Kind regards, Gabe