So far, unless we dive into virtual machines that video is not being rendered to be captured so there is nothing to capture. That's why it doesn't work.

So a workaround is to run an OS in say VirtualBox (any free Linux will do) then play that in your web browser on the virtual machine and do the screen capture in that virtual machine. It's too many steps to write a step by step so I'll leave this as a guide.

If it is on the web, many times you can download it just by asking. Be sure to ask the author for a copy.