Cannot see Firestick

[StujiC]

When I setup the Firestick last month it was working perfectly. Today no video. The capture card is working because I can see myself in the MacBook camera, but I cannot see the FS home screen. I’ve watched a half dozen videos , but no solution. All I see is the red boundary box when I plug in the FS. Occasionally, there is some video and audio from a NFL commercial that partially fills the screen. Thanks in advance. Stu