I don’t know if this will help you or not:
it’s called linux.
Given you like windows, try mint.
using W7 Pro on this laptop...
pinging for your enjoyment.
Perhaps to do this, Windoze uses the latest in graphics tech.
You could try turning off hardware graphics acceleration, and fool it.
I use showmore.com to capture screen video & audio. There is another piece of software called Debut which I have used and I rejected it. I’m happy with showmore.
What are you using the screen cap? Can’t you just hit print screen and paste into MSPaint? What about pausing the video and using snipping tool?
Perhaps it is because screen caps of films are copyright violations and are illegal.
Firefox has a Digital Rights Management check box under the General setting
take the shot with your phone.
The latest versions of Firefox also have some really great features for video card hardware acceleration of web pages. Look up how to turn hardware acceleration off in Firefox and that might also help. I’m not positive, but it has a good chance of being your issue if the capture worked before now suddenly does not.
Screenshot Captor. Ashampoo Snap. Lots of ways for free or cheap.
The last video card I bought had software bundled with it to record your screen when playing games. Maybe something like that would work.
https://beebom.com/how-to-use-windows-10-built-in-screen-recorder/
Try downloading the video using an add-on called Flash Video Downloader. I use it in Firefox. There are videos like at Amazon and at Youtube that stream. You get dozens or hundreds of small video files. You can combine them all easily with Movavi Video Suite 18 then export as say a mp4.
Use VLC to play and capture. https://www.videolan.org/vlc/index.html Right click on toolbar and click on Advanced controls. You have a button there for screen capture. Go to Tools> Preferences> Video to change where to save.
I came across this issue with blu ray movies using the player I think was called WinDVD. The answer was to strip the encryption then convert to another type if you want like mp4 or use another player that allowed you to make captures.
For videos you have on a disc try the Leawo Blu-ray Player
https://www.leawo.org/tutorial/how-to-take-a-screenshot-on-windows-1373.html
Tools to use:
Best video converter out there. Quick and you can easily edit the video. Big TIP. Install the trial version then go to uninstall. They will popup a big 40% discount offer. Buy it.
Movavi Video Suite 18
https://www.movavi.com/suite/?asrc=main_menu
DVDFab
https://www.dvdfab.cn
All the tech nerds use this - free opensourse....https://obsproject.com/