Why my car doesn't move?

So my question confuse me a few days;
I want to make some cars and they can move according to the roadmap.I read the tutorial https://docs.unrealengine.com/latest/INT/Videos/PLZlv_N0_O1gYup-gvJtMsgJqnEB_dGiM4/ and try to spawn cars like spawning batteris.It works but the car which I spawned can’t move.Then I set the car blueprint like this:

If I directly drag this blueprint to the level ,the car will move.But if I use the code like this:

	if (WhatToSpawn != NULL)
	{
		// Check for a valid World: 
		UWorld* const World = GetWorld();
		if (World)
		{
			// Set the spawn parameters
			FActorSpawnParameters SpawnParams;
			SpawnParams.Owner = this;
			SpawnParams.Instigator = Instigator;

			// Get a random location to spawn at
			FVector SpawnLocation = GetRandomPointInVolume();

			SpawnLocation.X += 2000.0f * i;
			SpawnLocation.Z = 100.0f;
			i++;
			// Get a random rotation for the spawned item
			FRotator SpawnRotation;
			SpawnRotation.Yaw = 0;//FMath::FRand() * 360.0f;
			SpawnRotation.Pitch = 0;// FMath::FRand() * 360.0f;
			SpawnRotation.Roll = 0;// FMath::FRand() * 360.0f;
			// spawn the pickup
			AVtestPawn* const SpawnedPickup= World->SpawnActor<AVtestPawn>(WhatToSpawn, SpawnLocation, SpawnRotation, SpawnParams);
			Vehicles.Push(SpawnedPickup);
			
			//UE_LOG(LogTemp, Warning, TEXT("MyCharacter's Name is %d"), Vehicles.Num());

			SpawnDelay = FMath::FRandRange(SpawnDelayRangeLow, SpawnDelayRangeHigh);
			GetWorldTimerManager().SetTimer(SpawnTimer, this, &ASpawnVolume::SpawnPickup, SpawnDelay, false);
		}

The spawned car then can’t move.Can anyone help me?