WILL NOT START BATTERY IS GOOD on 2003 Porsche Boxster

WILL NOT START, BATTERY IS FINE, USED THE CAR TODAY AND EVERYTHING WAS FINE

2 answers
Do you have any warning lights on? What about the dash lights, are they coming on? Do you hear a clicking noise when you try to start it?
the black box under the passengers seat has got water inside it from a leaking roof.... thats the problem i bet.....