findViewHolderForAdapterPosition() always returns null for custom ViewHolder

Question

So I'm having trouble getting the ViewHolder by adapter position. I'm using the LayoutManager to get the first completely visible item position, but when i call findViewHolderForAdapterPosition() it returns null. I'm also doing a check if postion is not -1. What am I doing wrong?

recyclerView.addOnScrollListener(new OnScrollListener() {
        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            int firstItemPosition = layoutManager.findFirstCompletelyVisibleItemPosition();

            recyclerView.postDelayed(() -> {
                if (firstItemPosition != -1) {
                    RecyclerView.ViewHolder currentHolder = 
                            recyclerView.findViewHolderForAdapterPosition(firstItemPosition);

                    if (currentHolder.getClass().isInstance(PremiumPostHolder.class)) {
                        ((PremiumPostHolder) currentHolder).startAutoplay();
                    }
                }
            }, 50);
        }
    });