I'm sorry for the inconvenience. If you get the "Mode Not Supported" message when you connect your TV to your device, it means that the video output of the device is set to a refresh rate or resolution that exceeds the TV's capabilities. Please consult the manual for your cable box or contact the manufacturer to determine how to correct the output signal.
-- HD Tech
I am connected to cable, my TV gets a blue screen with the message "Not supported Mode" and this will flash on and off with HDM1 in the upper left corner'
Sometimes the screen will go all snow or it will turn red, then back to the blue screen or back to the picture. I have checked all connections and there is a signal to the TV.