Stripe one time payments allow promotion code

I am going to implement a promotion code with a one-time payment. Stripe has announcement to use "allow_promotion_code=true" parameter on one time payments.

But something wrong with promotion input. Sometimes promotion code input didn't show up. Is there a bug for stripe or did I miss something?

  "id": "cs_test_b1IjCh7A8FGNDekAWtQZR93USCT2G3dxRe9zyLcGg7Qy3Ddt8yxxxx",
  "object": "checkout.session",
  "allow_promotion_codes": true,
  "amount_subtotal": 4140,
  "amount_total": 4140,
  "billing_address_collection": "required",
  "cancel_url": "http://localhost:8000/checkout?session_id={CHECKOUT_SESSION_ID}",
  "client_reference_id": null,
  "currency": "gbp",
  "customer": null,
  "customer_email": null,
  "livemode": false,
  "locale": null,
  "metadata": {
  },
  "mode": "payment",
  "payment_intent": "pi_1HxdH1CZvxxxxxx",
  "payment_method_types": [
    "card"
  ],
  "payment_status": "unpaid",
  "setup_intent": null,
  "shipping": null,