Assuming it has fuel, check for spark.

The spark plug is about a year and a half old. It still looks new. How do you know if it's bad?

It's fairly common for the fuel metering plug in the bottom of the fuel bowl to get plugged. Turn the mower up on it's right-side wheels (carb side up). Use a box-end wrench and take the plug out. The fuel bowl should remain stuck to the carb and no fuel should come out. Strip the paper off a wire tie and use the soft steel wire to clean out the three holes; large through-hole just above the bolt head, small metering hole in center of hollow bolt and small air bleed on the side at top of threads. After passing the wire through, blast holes out with spray carb cleaner. Put the plug back in, allow a minute for the carb to fill back up and try it. This only takes five minutes and usually is the problem. Use of a gas additive like Sta-Bil, Seafoam or Marvel Mystery Oil can help keep it clean. It may leak gas if you don't get it tight enough, but take it easy until you know how tight it has to be so it won't leak. It's a brass bolt into a zinc alloy and it won't take much to strip it. I use a little 4" box-end which restricts torque. There is also a magnetic kill switch that cuts the mower off if the mulch plug or bag is not installed, but you can test this by checking spark. If you have spark the switch is on. Basically, if you take the plug out and hold it against the engine while somebody pulls the starter cord, you should see and hear the spark. This more or less proves it's a fuel issue.

Thanks Saxman 1. You're right, seemed to be a fuel issue.