Hi Perez,
Based on my experience, service account MIIS_Service may called AAD_XXXXXXXXXX. Here is an example in my DirSync server:
Please check if the local DirSync administrator is the member of the local "FIMSyncAdmins" group.
Please Note: DirSync tool requires both 80 and 443 port, please check the firewall to allow the port.
Thanks,
Jason Jiang