I was having an issue like that, pretty similar.
It was asking for credential, was giving good one but always get out.
It was due to HPDP that didn't get the token from the DC and/or Mailbox server, and I don't have the link were I found the way of the solution.
Was with HPDP A.07.01 or A.08.00 (don't remember when I set this option).