My lawn mower won't start. The rope won't pull, well, it pulled once them nothing. There is gas and oil in the appropate places.Help I want to mulch leaves.

OK, what happened when it did this? Just to be sure, smell the oil to make sure no gas is in it, not saying you put it in the wrong place, but not knowing what brand and hp rating, it could've flooded with gas. Possibly hydro locking it on the compression stroke. Is it a ohv ( over head valve)? Anyway, take the plug out, make sure nothing is keeping the piston from moving. Otherwise, take the shroud off, and make sure the flywheel brake is working right, not grabbing the flywheel when you pull on the dead man switch on the handle. Then see if the flywheel can turn over by hand, with the switch if it works held onto. If that's all fine, check the recoil starter, the rope could've jumped the pulley and jammed