I'm finding this issue as well.. I'm a total newb to Playmaker and I'm following along on tutorial that uses the 'Smooth Look At Direction' Action using Playmaker 1.8 on Unity 5.3.
I've noticed that there are times when the Action is grayed out in the State tab of the Playmaker window.. While attempting to debug, I've unchecked and rechecked the FSM script that contains the Action and it seems to come back on during play of my build, but invariably the Action will gray out again and the functionality will be lost until I toggle to script again in the Inspector..
- J