You need your controller to posses the actor if it’s not done automatically by the game mode.
Pull out a pin from the return value of get player controller and type in posses, you should then get the node. Pass in the actor via reference that needs to be possessed.
Also your add mapping context needs to be hooked up to somewhere like a begin play node.
You have add the logic to the pawn you want to possess. So it needs to implement the input action IA_MoveBoth and use that action to drive the pawns motion or do a specific action via a function / macro