You have System Center 2012 Configuration Manager deployed in your organization, after you configure boundaries and discovery you found that none of discovered desktops/laptops/servers got ConfigMgr client installed and no site code assign to clients.
When you tried to push clients from site system, you received the following error:
Error: Some of the selected resources are not assigned to any site
Number of resources that are not in any site’s boundaries and will not be installed: xx
This issue may occur if boundary groups are not configured to use assigned site.
To solve this issue, make sure that you configured boundary groups to use site assignment as shown in the below figure: