Everything was good, then I imported some skyboxes from the package manager, and when everything recompiled, I got the same error in two locations:
Assets\PlayMaker\Actions\PlayerInput\PlayerInputActionBase.cs(10,27)
Assets\PlayMaker\Actions\PlayerInput\PlayerInputUpdateActionBase.cs(9,27)
error CS0315: The type 'PlayerInput' cannot be used as type parameter 'T' in the generic type or method 'ComponentAction<T>'. There is no boxing conversion from 'PlayerInput' to 'UnityEngine.Component'.
reinstalling does not fix it, and the Playmaker tab no longer appears at the top of the screen. I've got active input handling set to both, could that be an issue?