Zoho Desk API - Send Reply to CUSTOMERPORTAL

Zoho Desk API - Send Reply to CUSTOMERPORTAL

Hello!
I'll try to send a reply to Customer Portal, But the response is 500 (INTERNAL_SERVER_ERROR in service response).
  1. {"Error":"{\"errorCode\":\"INTERNAL_SERVER_ERROR\",\"message\":\"An internal server error occurred while performing this operation.\"}"}

Post Object:

  2. {
  3.   "channel": "CUSTOMERPORTAL",
  4.   "attachmentIds": [],
  5.   "to": "user@domain.com.br",
  6.   "fromEmailAddress": "user@zohosupport.com",
  7.   "contentType": "html",
  8.   "content": "HTML Content",
  9.   "isForward": "true"
  10. }
Reply in Emails works, but not register on Customer Portal.
Thanks in advance.