SubClient Creation > 406 Not Acceptable

Hello,

I'm trying to create sample SubClients on Sandbox with the following request:

POST /v4/clients/{id}/subclients/0570

Body:

{
  "name": "Alphabet",
  "tin": "01-1234567",
  "type": "C-Corp",
  "url": "www.google.com",
  "email": "[email protected]",
  "address": {
    "line1": "803 11th Avenue",
    "line2": "",
    "city": "Sunnyvale",
    "state": "CA",
    "zipcode": "94089",
    "country": "USA"
  },
  "phone": {
    "countryCode": "1",
    "number": "925577..."
  },
  "mcc": "1234",
  "mvv": "123456",
  "maid": "123456",
  "settlement": {
    "purchase": {
      "routingNumber": "",
      "accountNumber": ""
    },
    "disbursement": {
      "routingNumber": "",
      "accountNumber": ""
    },
    "fee": {
      "routingNumber": "",
      "accountNumber": ""
    },
    "exception": {
      "routingNumber": "",
      "accountNumber": ""
    },
    "serviceType": "N"
  },
  "fees": {
    "type": "MDR",
    "monthlyMinimumProcessingFee": "",
    "authorizationFee": "",
    "deleteFee": "",
    "purchaseFeeFixed": "",
    "purchaseFeeVariable": "",
    "purchaseFeeCap": "",
    "disbursementFeeFixed": "",
    "monthlySubClientFee": "",
    "chargebackFee": "",
    "retrievalFee": "",
    "batchFee": "",
    "cardTypeFee": {
      "intlCreditFixed": "",
      "intlCreditVariable": "",
      "intlDebitFixed": "",
      "intlDebitVariable": "",
      "creditSurchargeFixed": "",
      "creditSurchargeVariable": "",
      "amexFixed": "",
      "amexVariable": ""
    },
    "3DSFee": "",
    "accountUpdaterFee": ""
  },
  "reserveAccount": {
    "routingNumber": "",
    "accountNumber": "",
    "calculationsCurrencyCode": "",
    "calculationsVariable": "",
    "calculationsFixed": "",
    "calculationsNoOfDays": ""
  }
}

Response:
406 Not Acceptable

Body:

<html>
  <head><title>406 Not Acceptable</title></head>
  <body>
    <center><h1>406 Not Acceptable</h1></center>
    <hr><center>nginx</center>
  </body>
</html>

Ensured we're provided everything required in docs: https://developers.tabapay.com/reference/createsubclient

Any pointers would be deeply appreciated. Thanks!