The IsValid node in pic1 does not have an object plugged in, it will never fire through the Valid pin. You should plug in MyDamageAttack there.
This does not mean it will work, though. The MyDamageAttack object reference is simply invalid (empty, it does not seem to point to any object), how did you reference it?
Creating a reference variable is not enough, you still need to point it to a specific object.