Hi,
I'm having the same issue.
I was typing in "set float value" into the action browser, and halfway through the action browser went blank. Everything else works, but I can't work on FSMs, because there's no action browser now.
I get this error:
InvalidCastException: Cannot cast from source type to destination type.
OnAnimatorUpdateActionEditorBase.EditEveryFrameField () (at Assets/PlayMaker/Actions/Animator/Editor/BaseClasses/OnAnimatorUpdateActionEditorBase.cs:18)
SetAnimatorFloatActionEditor.OnGUI () (at Assets/PlayMaker/Actions/Animator/Editor/SetAnimatorFloatActionEditor.cs:20)
HutongGames.PlayMakerEditor.ActionEditor.OnGUI (HutongGames.PlayMaker.FsmStateAction action) (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/ActionEditor.cs:196)
HutongGames.PlayMakerEditor.ActionSelector.DoSelectedActionPreview () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/ActionSelector.cs:589)
HutongGames.PlayMakerEditor.ActionSelector.DoBottomPanel () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/ActionSelector.cs:546)
HutongGames.PlayMakerEditor.ActionSelector.DoGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/ActionSelector.cs:158)
HutongGames.PlayMakerEditor.BaseEditorWindow.OnGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/BaseEditorWindow.cs:72)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
I followed instructions (from a post from Feb 2017 that looked identical to my situation) of getting the Pathfinding package from the Ecosystem, but it's made no difference. I did move a prefab to a new folder, as it was sharing one with another prefab that had the same material, and this brought my action browser back briefly, but it disappeared again as soon as I started typing in it.
I'm working through M Dot Strange's Playmaker tutorial, Lecture 49, if that helps at all.
Any help would be appreciated.