Try adding a scene component to your class
UPROPERTY(EditAnywhere, BlueprintReadWrite)
USceneComponent* Root;
and inside of the cpp initialize it in the CDO (AMovingPlatform ::AMovingPlatform() )
Root = CreateDefaultSubobject<USceneComponent>(TEXT("root"));
You should then be able to move it.
The first component that registers will automatically become the root component.