When trying to authorize a DHCP server, you may get the following error:
The authorization of DHCP Server failed with error code 5 – Access is denied
This may happen even though you’ve specified credentials with authority to authorize the DHCP server.
The reason for access to be denied is that the account you are running the DHCP Post Configuration Wizard with is not an Enterprise Admin.
To fix this, log out of Windows and log in with an AD account that is a member of the Enterprise Admins group within the domain you are trying to authorize your DHCP server with, then authorization of the DHCP server again from this account.