* Turn the 10 year old 3008WFP off
* Disconnect every cable from the 3008WFP including the power cable
* Press and hold in the 3008WFP power button for 8 seconds
* Reconnect only the power cable to the 3008WFP
* Turn the 3008WFP on. The floating "No cable" dialog box should appear on screen against a black background. How does it look?