First, an SV600 is a Kohler Courage, not Briggs.

Possibly the plunger on the carb fuel solenoid has stuck.
Make sure the solenoid is getting 12V with the key ON.
Listen to it when switching the key ON/OFF/ON.......
It should CLICK.

Yes you're right, sorry about that. Kohler. I had B&S on my mind. (chuckle) I forgot to mention I had checked the fuel solenoid. It is working. It throws me that he mowed nearly an acre and we loaded the mower on the trailor the next day. Hate to admit defeat.

would chk for a sheared crankshaft key. Timing off.

Well, it appears as if the key is sheared. Don't have time to pull it today but will tomorrow. Will post results if it's anything but the key. Thanks for the help. I did not realise how it could be the key from the timing of the shear. He mowed nearly an acre and it must have sheared as he drove it into the shed. Thanks for the help.

Aside from an internal parts failure suddenly stopping the crankshaft rotation, the greatest load on the key is imposed during cranking of the engine if the flywheel is the least bit loose or untight (meaning the retention nut/bolt is not torqued to specs).
If the flywheel is not as tight as it needs to be, the torque load of cranking will be passed directly to the key (instead of directly through the flywheel to crankshaft as designed) and the key will shear.

Hmm..The key was sheared thanks for the insight there. However I replaced it and the machine still doesn't want to start. Has fuel and spark but the spark isn't a real strong looking one. Trying to re-group. What am I missing?

pull engine shroud cooling sheet metal. look for trash/mouse nests. look for evidence of damage to ignition wiring including being chewed by rodents. when correct, you should see a bright blue-white spark jump across spark plug.
If someone has gone wild with a garden hose or power washer , you may have elect problems anywhere. L&g tractors can't stand being drowned..

Cleaned the pick ups on the fly wheel and reset the gap. Fired right up. Thank you guys for your help. Good to have a place to turn to.

feedback much appreciated.