Error with MercadoPago payment preference

Question

I'm trying to implement MercadoPago in my application. However I'm facing an error on the payment screen. I first create the payment preference with the CURL below using the Sandbox access_token, from the API response I retrieve the sandbox_init_point which contains the payment URL.

When I try to pay with that URL I get the error "Tuvimos un problema, intenta nuevamente". I've tried this with Test User and a Real Email, I also tried the Sandbox access_token and Production one with the same results.

I'm quite sure I'm creating the preference correctly since the CURL was copied directly from MercadoPago documentation. What can be causing this error?

CURL

curl -X POST \

  'https://api.mercadopago.com/checkout/preferences?access_token=MY_TOKEN' \

  -H 'content-type:application/json' \

  -d '{

  "items": [

    {

      "title": "Dummy Item",

      "description": "Multicolor Item",

      "quantity": 1,

      "currency_id": "ARS",

      "unit_price": 10

    }

  ],

  "shipments": {

    "mode": "me2",

    "dimensions": "30x30x30,500",

    "receiver_address": {

      "zip_code": "5700",

      "street_number": 123,

      "street_name": "Street",

      "floor": 4,

      "apartment": "C"

    }

  }

}'

Error Message