UInstancedStaticMeshComponent does not showing static meshes

For a few days I am trying to solve one problem with using UInstancedStaticMeshComponent. I have created class based on AActor.
Add as property some variables:

UPROPERTY(VisibleAnywhere, BlueprintReadOnly)
class UInstancedStaticMeshComponent*    InstancedArrowsMesh;
UPROPERTY(EditInstanceOnly, BlueprintReadWrite, Category = "Arrows")
int32    CountArrows;

In the constructor I’ve write the next strings:

InstancedArrowsMesh = CreateDefaultSubobject<UInstancedStaticMeshComponent>(TEXT("InstancedArrowsMesh"));    
InstancedArrowsMesh->AttachToComponent(StaticMesh, FAttachmentTransformRules::KeepRelativeTransform);    
InstancedArrowsMesh->InstancingRandomSeed = 26425;    
CountArrows = 3;

At the function BeginPlay I have write the next strings:

const int32 nMaxArrowCount = ArrowSpawnArray.Num();      
for (int nArrowIdx = 0; nArrowIdx < CountArrows; nArrowIdx++)    
    if (nArrowIdx < nMaxArrowCount)        
        USceneComponent* sceneComp = ArrowSpawnArray[nArrowIdx];            
        if (sceneComp)            
            FTransform    instanceTransform = sceneComp->GetRelativeTransform();                

After that, I’ve created blueprint class based on my C++ class.
If I am adding that blueprint class on sceen directly (using drag’n’drop) everthing is fine. After launch the game I see my object with Instanced Static Meshes objects. But if I spawn my object dynamicly using GetWorld()->SpawnActor(…) function I am seeing my object too, but without any instanced static meshes within.
What is wrong? What I have missed?
When I debugged this feature, everthing is fine, BeginPlay function is called and my Instanced Static Meshes added successfully. I have no idea, what I have missed

Please help me with it !!!