dead battery

My 2015 RX7320PC all of a sudden won't start. When I turn the key, no sound, no dashboard lights, nothing. I've checked to ensure that it's in neutral and that all lights are off. I put a trickle charger on it and left it overnight. No change. I put my battery charger on it. Not able to get it...

Battery fully charged. No clicks when key is turned on. No headlights. No power to solenoid. Nothing. Is this a bad ECM?

I recently purchased a Cub Cadet Zero turn mower from the dealer last spring. It was a new mower previous years stock carry over. I only put on about 10 or 15 engine hours on it last year. It has the24 H.P. Kawasaki FR 730V Engine. When I was at the dealer it wouldn't start & the battery had...