If you do not have a matching profiling policy, you can assign an unknown profiling policy. The endpoint is therefore profiled as Unknown. The endpoint that does not match any profile is grouped within the Unknown identity group. The endpoint profiled to the Unknown profile requires that you create a profile with an attribute or a set of attributes collected for that endpoint.
https://www.cisco.com/en/US/docs/security/ise/1.0/user_guide/ise10_man_identities.html

Section: Endpoint Compliance
Explanation/Reference:

Explanation:
https://www.cisco.com/c/en/us/td/docs/security/ise/2-
4/admin_guide/b_ise_admin_guide_24/b_ise_admin_guide_24_new_chapter_011.html Step 1 Choose Administration > System > Deployment.
The Register button will be disabled initially. To enable this button, you must configure a Primary PAN.
Step 2
Check the check box next to the current node, and click Edit.
Step 3
Click Make Primary to configure your Primary PAN.
Step 4
Enter data on the General Settings tab.
Step 5
Click Save to save the node configuration.