Internal server error when saving card in paypal vault

Question

I am using pay-pal vault to store my users credit card. When am trying to store user credit card am getting internal server error with response code = 500. I have tried with different type of sample test cards, but still it is not working for me. Please save me from this issue.

credit_card = {
        number: "5183330730754255",
        type: "mastercard",
        expire_month: 11,
        expire_year: 2018,
        cvv2: "874",
        first_name: "Joe",
        last_name: "Shopper",
        billing_address: {
            line1: "52 N Main St.",
            city: "Johnstown",
            country_code: "US",
            postal_code: "43210",
            state: "OH",
            phone: "408-334-8890"
        },
        external_customer_id: "nodedeveloper122"
    }
    result = Typhoeus.post(
        'https://api.sandbox.paypal.com/v1/vault/credit-cards/',
        :params => credit_card,
        :headers => {"Content-Type" => "application/json", "Authorization" => "Bearer ************"}
    )