Cannot update shipping addres at checkout with Storefront API

Retired Boards Appdev Graphql Basics And Troubleshooting
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1

Hi there! I’m trying to create a checkout with storefront, and neither the mutation checkoutCreate nor checkoutShippingAddressUpdateV2 will let me add shippingAddresses. When trying to perform a mutation, all I receive is null without much more info. An example of a mutation would be

mutation CheckoutShippingAddressUpdateV2 {
      checkoutShippingAddressUpdateV2(
        checkoutId: "gid://shopify/Checkout/CHECKOUT_ID",
        shippingAddress: {
                address1: "Address",
            address2:"null",
            city:"City",
            company: "null",
            country:"Spain",
            firstName:"M",
            lastName:"Godoy",
            phone: "+16135551111",
            province:"Madrid",
            zip:"0000",
        }         
      ) {
        checkout {
          id
          shippingAddress {
              address1
          }
        }
      }
    }
2

Forgot to check for userErrors and checkoutUserErrors. I’m too early in the development of this store and payments are not set up