Territory assignment setup for service-Username is not visible to add territory administrator role.

 I am starting territory setup in the application and I understood to give roles to the user are  territory administrator,Territory management.

In User Management responsibility these roles can be assigned.

Problem is when I have searched username under User Management Responsibility then username  is not populating with User details and assigned role.

How I can get details?

User already created in Sysadmin also user has Support role,user role is visible at CRM HTML administrator.