Hi, I have a exmark lazer turn 27 HP and love it. Got a problem yesterday, it was running fine picking up leaves ( rear bags) and ran out of gaz , it shut off naturally.......got some gaz, filled it and went to start it , turn the key, nothing, battery id fully charged, get juice to the starter. All safety start are on, seat, levers and park lever is up position. Any idea what it can be?