xt40 won't start

[wackman]

I jumped in my xt40 tonite and turned the key. everything lit up as normal, lights as normal, when the plugs were ready, I turned the key to start. made a click to start, then nothing. Now when I turn the key on, the lights come on, but when turned to start, it makes no sound, and doesn't do anything. the battery shows a full charge with my meter, what could cause this all of a sudden failure? TIA

 

[Tazza]

When you turn the key, do the lights dim?
Batteries do just go dead. They may read a full 12v but under load they will drop to zero.
I'd start by jumping a known good battery to it, at least if it starts to crank you know it's the battery.