Apple TV A1842 is flashing after power cut

First, please try a cold restart (unplug from power for 30 seconds or so). Sometimes that is enough to get back in working order.

If that doesn’t result in a normal startup sequence, then please contact Apple Support to “get service” on your Apple TV A1842 unit.

Reference: If you see a flashing indicator light on Apple TV 4K - Apple Support

Unplug it, wait ten seconds or so, and re-plug it, and see if things work better.

If that fails, try (if you can) a reset: https://support.apple.com/en-us/108897 (home and menu buttons together, IIRC)

If that fails, you’re headed for repair or replacement.