Cannot crop window


New Member
I am a new user trying to copy a window, a video playing in a browser, updated Firefox, and would like to crop to record only the part of the browser window with the video content. I tried clicking Window Capture +ALT, and other combinations but I cannot get the red box to show. Tried Filters, Copy/Pad cannot get this to work. Numbers I enter seems to make no difference. I have searched the forum and found many entries but none that would help. I would appreciate any help.