Apple TV 4K Not Responding - Blinking Light

ATV was unplugged for a month - since plugging it back in the box blinks at 1 blink / sec with an occasional 2-3 blink flurry every 10 or so blinks.

Have plugged / unplugged, charged the remote (black), pressed and held "Menu / +" buttons 3 inches from the unit, and attempted to connect with Control Centre from my iPhone -

Every 2sh minutes a "Apple TV is now available" banner appears on the top right of the TV screen but nothing I've done has enabled the menu to appear.

Wondering if it was bricked by an errant Apple OS / firmware update?