Welcome to the forum!
What do the plugs look like when it won't start? How fresh is the gas? Is the gas turned on?
It could be flooded. If so, underneath the exhaust manifold, there are three small plugs. If you remove those, that will drain the crankcase. You could also pull all three plugs and pull the rope to clear the crankcase and cylinders of excess fuel. It may take 15-20 pulls to get rid of any gas in the crankcase. You may see a mist of fuel leaving the spark plugs, that would indicate fuel in the crankcase.