Instead of:
PickUpBox->AttachToComponent(PickUpRoot, FAttachmentTransformRules::SnapToTargetNotIncludingScale);
Try:
PickupBox->SetupAttachment(RootComponent);
Instead of:
PickUpBox->AttachToComponent(PickUpRoot, FAttachmentTransformRules::SnapToTargetNotIncludingScale);
Try:
PickupBox->SetupAttachment(RootComponent);