Why do I not have "OU" and "Mappings" tabs in my ADmitMac settings?

These settings only appear if you join the Mac to an Active Directory (AD) domain using the Fully Qualified Domain Name (FQDN). If you join the Active Directory domain using the short name (NetBIOS name) of the domain, ADmitMac will assume it is an NT domain. To join it to the AD, you would need to remove the current domain binding and join it using the FQDN.

If your network is not Active Directory (when you join the computer to an NT domain network) those options are not available in the ADmitMac Directory Access Plugin properties.