Why doesn't my bike want to start

My Honda Motorcycle VFR 400 had been riding just fine after the day I got it back from a major service,...the morning after,...it wouldn't start...

I took it back to the mechanic,...he said he stripped the tank and wiped the plugs and it worked just fine the day I got it back...and I started it the morning after,...but in the evening when I got back from work...it wouldn't start again...