Sounds like it could be a few things, but most likely is that the pickupcube actor only has one component - the cube itself. This means that that component has no relative transform, as the transform for the cube is one and the same as the transform of the object, not its relative offset to the actor.
To correct this, you could probably add a scene component to the actor and make the cube a child of that component and the scene component the root component of the actor. This will allow the cube to move relative to the scene component, so your timeline should work.