If you are running CRM locally and you try and add a new user and you get this error:
Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: Server was unable to process request.Detail:
<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">
-2147016646
<ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />
Server was unable to process request.
2017-08-25T10:49:59.5445312Z
The error here is this section:
-2147016646
This is a domain controller error which says the server is not operational, which is weird as people can login but new users cannot be added - weird hey???
Once I did some investigation I noticed CRM trying to call a domain controller which was no more, so I found this registry hkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSCRM
You will notice a key called: PreferredDc
If you set this key ensure it points to a valid domain controller, in our case this pointed to a domain controller which was no longer a domain controller
If you do not have this key then CRM will auto discover the domain controller.