Not sure which engine your mower has on it. But, if i have a starting problem i remove the air cleaner and spray a short burst of carb cleaner in the carb. throat. If it starts and only runs a few seconds then you have a fuel system problem. If it don't start, then possible electrical problem.

Since Toro has a five year guaranteed to start warranty on this mower, take it back to the dealer and tell him you want Toro to stand behind its warranty and fix the problem.

I don't see where you put fresh fuel back into it... A couple shots of carb spray may relieve your blues and it up and runs as nod was saying. I find the auto chokes stick every once in a while during storage or many times a touch of water or old fuel is in the bowl of the carb. The moral of the story is that unless you removed the bowl to remove the last bit of fuel- there was some left. Treating the fuel with a stabilizer adds a level of safety against this happening in the future. Toro's starting guarantee I don't believe covers old or contaminated fuel issues. Best of luck.

As Tom advises a ounce of prevention is what is required . Pull your spark plug and ground it against the cylinder or metal shroud . Check for good blue spark . If not replace with new plug and retry . If all ok then spray some carb cleaner in the carb or plug hole and attempt to restart . If it starts then fuel restriction was the key . Refill wih fresh fuel and add 2 ounces of concentrated fuel cleaner . Let fuel and cleaner mix sit for approx 30 minutes then attempt to restart . 90 % of the time any gum or varnish is removed allowing engine to start gradually respond as normal . In the future again as Tom has suggested use a fuel stabilizer like Star*tron available at Walmart or Stabil...etc at the very least ..