Remote Desktop Connection Denied because the user account is not authorized for remote login
Solution 1:
Create a group policy that uses the restricted groups feature to place "Domain Users" in the "Remote Desktop Users" group. Apply that policy to your server, overriding the local policy. Log in as domain admin and make sure the policy refreshes. When you examine the remote desktop users group, verify that "domain users" has been placed in this group. Now, log off and test as one of your domain users.