To sing in remotely, you need the right to sign in through Remote Desktop Services

After the server  has been promoted to a domain controllar, when trying to open Local Users and Gropus (lusrmgr.msc) console, it returns the following error:

The computer xxx is a domain controllar. This snip- in cannot be used on a domain controllar. Domain account are managed with the Active Directory Users and Computers snap-in.

To allow connection to the domain controllar member to the Remote Desktop users group you need to:

• Start local policy editor (gpedit.msc).
• Go to Computer ConfigurationàWindows SettingsàSecurity SettingsàLocal Policiesà User Right Assignment.
• Find the Policy Allow log on through Remote Desktop Services.

• Edit the Policy by adding the local group Remote Desktop Users (like this: Domain Name\Remote Desktop Users), a `domain user, or a group (like this: domain\some group name) to it.

• Run the update of the local policy in command prompt.
• Gpupdate /force
• Reconnect RDP.