it seems something messed up with your PM, why don't you
1. go to C:\Users\User\AppData\Local\Unity\Asset store
and locate your PM folder it is under hutong games and delete it
2. then redownload Playmaker from asset store (it is brand new 1.9.1 and tons of improvements too)
3. delete Playmaker on your project and when you're done, import it from the package manager
4. it should solve your problem
Good Luck