What about the Woodruff key on the crankshaft/flywheel?
If it shears, you get no spark.
Hitting rocks, stumps, roots, big sticks, etc, will cause damage to the key.
Do both the flywheel and the crankshaft turn when you pull the starter cord? If not, you likely have a sheared woodruff key.
Sheared woodruff keys are a common cause of "no spark" on walk behind mowers.