I'm attempting to post contact information into the API from my lead distribution software when someone fills out one of our forms. It worked fine when I was just posting name and contact email, but once I added custom fields, I am receiving an error response that says Unauthorized request. Is there something I need to pass to allow adding custom fields to the subscriber list? Below is what I posted, many fields are blank, but that obviously shouldnt matter. I've made sure to triple check the authtoken and listkey  for my account. The xxxx is just me masking my authtoken and listkey. I've also posted with and without spaces between the xml fields. 

Request URL:  
https://campaigns.zoho.com/api/xml/listsubscribe?authtoken=xxxx

Post Parameters:  
scope=CampaignsAPI&version=1&resfmt=XML&listkey=xxxx&contactinfo=<xml> <fl val="First Name">Tim</fl> <fl val="Contact Email">dnky67@hotmail.com</fl> <fl val="dob"></fl> <fl val="ip_address">98.109.103.50</fl> <fl val="property_value"></fl> <fl val="mortgage_balance"></fl> <fl val="credit"></fl> <fl val="property_type"></fl> <fl val="mortgage_rate"></fl> <fl val="age"></fl> <fl val="spouse_age"></fl> <fl val="spouse_first_name"></fl> <fl val="spouse_dob"></fl> <fl val="loan_amount"></fl> <fl val="in_school"></fl> <fl val="student_loan_type"></fl> <fl val="credit_card_debt"></fl> <fl val="student_loan_debt"></fl> <fl val="employed"></fl> <fl val="current_paycheck_garnished"></fl> <fl val="current_irs_offset"></fl> <fl val="loans_in_default"></fl> <fl val="tax_debt_amount"></fl> <fl val="payment_program"></fl> <fl val="vertical">Student Loan</fl> <fl val="Last Name">Wise</fl> <fl val="Phone"></fl> <fl val="Address"></fl> <fl val="City"></fl> <fl val="State"></fl> <fl val="Zip Code"></fl> <fl val="Mobile"></fl> </xml>

Post Response
<?xml version="1.0" encoding="UTF-8" standalone="no"?><response uri="/api/xml/listsubscribe" version="1"><code>1007</code><status>error</status><message>Unauthorized request.</message></response>