RingCX Scripting Studio WWW tool doesn't work (Zoho)

Since Zoho CRM for RingCentral isn't supported by RingCX, I'm trying to call the Zoho CRM API using the WWW tool in RingCX Admin to find a contact using a phone number. No matter what I pass in the header, I get this error:

 {
  "readyState": 0,
  "status": 0,
  "statusText": "error"
}

Is there something I can do so I can get a non-error result in this tool? The exact same call works fine in Postman...