Last videos I tried today was some movie trailers, that's what I usually use YouTube for, I think it's nice to watch a few trailers before I start a movie to "get in the mood"
Specifically I did a search for "movie trailers" and tried to play "Suicide Squad Official Trailer #1", "Deadpool Official Trailer #1" and "BATMAN V SUPERMAN: DAWN OF JUSTICE Official Trailer #4". They all play in Standard View, but not in Theater View.
I agree the problem probably is connected to something else on my computer since it works on other machines. I did try both browser engines also in Theater View. I tried clearing both IE and Chrome cache, cookies, etc. So the problem might be some setting in MC carried over from an old version. I could try to reset all MC settings to default and opt to not import settings when importing the library and see if that helps, but it will take some time doing all the settings over again manually, and I'm going away for a week tomorrow and won't have time to do that until I get back. If you have any idea of any settings I could try and change, let me know.
I tried something I haven't tried before, adding a YouTube video to my library without downloading, and it played fine in Theater View. Obviously I played it through Video -> Genres in Theater View where it showed up together with my other video files on my computer.
I do have a few services stopped or disabled in Windows 7, so if there's any specific service Theater View YouTube needs, I could check that.
Also tried enabling every single feature in MC (Under General -> Features) but that didn't help either.
Any registry entries I could check? Maybe remove some old ones that aren't in use anymore (if they got copied over from previous version's registry entries)?
I currently don't have any other antivirus or firewall installed except for Windows Defender and Windows Firewall. Tried disabling both.