I didn't see any configuration issue from the information you provided.
I agree with you that the issue is between HPDM and FTPS server. Could you please check the whitepaper of HPDM 4.7_ftp_Configuration to see if there is any difference in your FTPS server configuration? You can easily get it from Help button on HPDM Console.
I have my environment in hand and I can connect with IIS FTPS server successfully by stricktly follow the white paper.