Apple TV error msg No signal. Light stays on, unresponsive

My 4K Apple TV's power light is on but my screen is blank except for a message: “No signal. Check the external input or select another input using the INPUT button.”

The external input is exactly as it has always been.

when I press the remote's power button the light goes off for as long as I hold the button down. Then when I release it the power light comes on and remains steady with that original error message.

i have tried Power/Menu simultaneously, and also physically unplugging it, waiting, then plugging it back in. The unit remains unresponsive, its power light constantly on.

My hunch is that the Apple TV hardware unit has failed. My Sony TV's other inputs including Android are working properly.