P2219H, no longer recognizing PC

I purchased this P2219H only a few months ago is not recognizing DP or HDMI signal from my desktop and laptop. I have tried replacing all cables and even using the same cables on an identical, working second P2219H, but this first P2219H still is having trouble recognizing signals. The only function the P2219H buttons currently have is Input Select. When either the Confirm or X button is pressed, the P2219H promptly sleeps.

What steps can I take to get the P2219H to work again?