Most likely it is a fuel problem - no fuel getting into the cylinder. Remove the air filter and drip some gas into the carb throat. See if it will run on that gas, which eliminates many other possibilities. Did you run stabilized fuel through it before storage? Is your gas fresh? Another trick is to pick up the mower near the carb and drop it from about 6". This frequently will shake the stuck float loose. Once you get it running, always use an additive that stabilizes the fuel and cleans the fuel system, like Seafoam. I also add 1 oz:1 gal of Marvel Mystery Oil to my 4-cycle fuel and twice that to my 2-cycle brew.