Sometimes when you install a Lync setup and change the server, you might have problems when adding the clients back to the newly created server. Some issues might be that that you cannot log in or mostly you get an error on the management panel on Lync when you enable a user as below:
"RegistrarPool" with identity "1234567890" assigned to "sip:firstname.lastname@example.org" has been removed from the configuration store.
You may also encounter the error,
Cannot move user in enable operation. Use the Move user cmdlet instead
To cleanup the user you will need to edit the Active Directory schema. Open the ADSI Edit from your domain controller. Connect as the Default naming context, find the user you need to change (in this case sysadmin) and select properties. Change the below properties to either blank or
After you set the below, exit the ADSI Edit and retry on Lync. The user should be able to work.