SixRui

> Even VLC UWP or any other media player app that registers `.mp4` extension? Yes, I installed VLC, not VLC UWP. There was no problem.

> Can you check VLC UWP since VLC doesn't use a manifest/msix nor it's installed by the store. Unfortunately, VLC UWP has the same problem with the same error info...

> Right, is this a stock Windows install? Have you change any services running status or installed a "debloater" app? I didn't modify any system settings or services on purpose.

> Is this device under an organization? Maybe some security product is locking that (and more) registry keys? personal device. any possible workaround?

> Personally I would recommend a full reinstall but I understand how time-consuming it can be and there might be some simple solution but without more information it's hard to...