Cannot add one-off charges to a cardless trial subscription

{
  "error": {
    "type": "request_error",
    "code": "subscription_one_off_charges_not_allowed_on_cardless_trial",
    "detail": "One-off charges can't be added to a cardless trial subscription before a payment method is added.",
    "documentation_url": "https://developer.paddle.com/errors/subscriptions/subscription_one_off_charges_not_allowed_on_cardless_trial"
  },
  "meta": {
    "request_id": "00000000-0000-0000-0000-000000000000"
  }
}

Details

Status code

400

Error code

subscription_one_off_charges_not_allowed_on_cardless_trial

Error message

One-off charges can't be added to a cardless trial subscription before a payment method is added.

Common causes

• You're trying to add a one-off charge to a cardless trial subscription before the payment method has been added.

Troubleshooting

• Add a payment method to the subscription, then retry the request.