with a speed of 0 (this is NOTworking!)
But you’re not even trying to set velocity to 0 in your BP, of course it doesn’t work =)
If your ball simulates physics, try SetPhysicsLinearVelocity, and you probably want to SetPhysicsAngularVelocity too;
If it’s a pawn with a movement component, you can use StopMovementImmediately for the movement component.