Apple Pay - Payment is null when fetched for readystatus

[lorenzOliveto]

I'm trying to implement the apple pay checkout but I'm facing this issue: when I query for the payment to check if it's been completed it returns nil so the checkout always fails.

This is the query

Storefront.buildQuery(inContext: context) { $0
    .node(id: paymentId) { $0
        .onPayment { $0
            .id()
            .ready()
            .errorMessage()
        }
    }
}

I'm sure that the payment id is correct since I've taken it for the checkout previously.

What could cause this problem? How can I query for errors on this operation?