Importing Users from AD

Check if PAM360 is installed in a member server or a workgroup machine. Member servers will by default have connectivity to AD and if it is a workgroup machine then there should be a connectivity available from workgroup machine to primary domain controller.
Check if the PAM360 service is running with a service account.
Check if the PAM360 server has connectivity to the domain controller.
Check if the DOMAIN field of the import page contains the correct NETBIOS name in upper case.
Check if the FQDN supplied in Primary DNS name field is correct and reachable from PAM360 server.
Check if the customers Active Directory has SSL mode enabled. If so, then copy the SSL certificate of the domain into PAM360/bin directory and run the importCert.bat command to import the .cer file. For example, importCert.bat MEAD.cer.
Request the customer to get the certificate of Domain to run the above command.
Unless importing one or few users, always use the "Fetch Groups and OU's" button at the bottom to fetch the actual Groups/OU's from AD and select them for import.
If you see the message "Users not imported" with a few users listed under it in red color, then it is definitely a permission issue. So change the login account used in the import page with a different account(preferably a domain admin) and try the import again.
While trying to import a group, if you see the message "Group list is too big to display", then stop the PAM360 service, edit the file named system_properties.conf present in PAM360/conf directory and look for the line domain.group.limit=2500. Change the value 250000, save the file, start the service again and try the Fetch Groups and OUs button again. Similarly for OU's check for domain.ou.limit=2500 change the number based on the customers AD size.