Using C# HttpWebRequest API to submit this. Have everything filled out according to this webpage. Even using Chrome’s Advanced REST Client to manually submit and still have same problem.
Triple checked the HTTP Method=POST, Headers: content-type=application/x-www-form-urlencoded and content-lengthPortal ID, Form ID, message payload using encoding and without, hs_context.
Any ideas what could be wrong? Can share more information individually if someone can help.