I'm getting a flashing screen on my monitor

I started my machine and I am getting a flashing screening on my monitor. I checked all the cables and I’ve found nothing. I ended up replacing all the cables but still have the same problem. When I unplug all the cables except the HDMI the remote works fine, when I plug in the other cables the remote starts blinking and can’t be programmed. I’m thinking the controller box is broken. I can’t think of any other fixes. Any thoughts?
Thanks Chris