Domain 2008r2 Domain Administrator does not have permission

User A in the Domain Admins group does not have the local administrator permission on the Domain Server "1" (not a DC, 2008r2 system. However, the Administrator account has permissions by default.
You cannot add a to 1 administrator group. The description is already in this group.
Where is this problem?

Is the account newly added to the domain Admin group?
Log out, log on again, and try again?

In the entire Domain Admins group, there are only two users, one being administrator and the other being "". Not only did I log out n times, but also restarted n times. However, a does not have the permission or even the permission to change the IP address.
Tested. Only Domain Admins group permissions are retained for group A, not in any other group. Get the same response.
Reload the DC, redo the domain, and re-Add the domain. This is the case.

The reason is that the two 2008r2 instances used as the domain controller and the added domain have the same SID (clone virtual machine or ghost system ). You just need to reinitialize the system with sysprep on one of the machines and then add it to the domain.

This article from the "technical capital" blog, please be sure to keep this source http://692572.blog.51cto.com/682572/1433625