As I had this issue month ago I’m not sure if I remember correctly, but I think it eventually worked (Player was possesed), but there was no change in GUI of Pawn properties (property in gui remained Disabled).
I will try to refresh my memory in some spare time.
I was finding this problem to be the case with the “Player Input and Pawns” tutorial. I put breakpoints in the MyPawn constructor so I could see that AutoPossessPlayer was correctly being changed from 0 to 1. But another breakpoint in APawn::PreInitializeComponents() showed that when it gets there AutoPossessPlayer was already been reset to 0. I searched the entire solution and did not find anywhere that it would be setting it to 0, so I did’t know why or where it is being cleared.
Finally, I deleted the MyPawn that was in the level and dragged the class into the viewport to create a new one. After that it worked, so somehow the instance that was in the level got messed up.