I have gone through all the steps to authenticate using OAuth 2.0 server flow as seen in the documentation here https://v3.developer.constantcontact.com/api_guide/server_flow.html This is all working fine and I'm able to get the access token and refresh the token every hour without problems.   But, when I attempt to do a curl post to add/update a contact in a list I get this message returned {"error_key":"unauthorized","error_message":"Unauthorized"}   Below is the url and headers I'm using $aTokenValue being the access_token curl_setopt( $ch, CURLOPT_URL,"https://api.cc.email/v3/contacts"); curl_setopt( $ch, CURLOPT_HTTPHEADER, array('accept: application/json')); curl_setopt( $ch, CURLOPT_HTTPHEADER, array('authorization: Bearer '. $aTokenValue)); curl_setopt( $ch, CURLOPT_HTTPHEADER, array('cache-control: no-cache')); curl_setopt( $ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));     any guidance provided would be extremely helpful! Thank you in advance ... View more