Hi,
Since you are using the target actor as condition, you need to set it at some point, may it be when your pawn see the player or any other event.
To set the blackboard key, it is different if you do it in a task or in an actor.
Here it sets the value from the AI character :
And from inside a task :
Set it to nothing and your pawn will return to his patroll.
Don’t forget to check all your tasks and decorator in the BT, they need to have correct keys associated