Get rid of the "Trigger Once" (which should always be at the bottom) and the "For Each" and just have:
Enemy hp is 0 or less - destroy enemy
On Enemy destroyed - Add X to Xp
I don't understand why that shouldn't work. I'd have to see the cp3 file to see what's wrong.
tomologames(at) gmail . com if you want me to take a look at it.