Unable to enable Remote Access for User outside of LAN

I have a client who needs to use a computer via Remote Desktop using mail.FQDN.com/remote.  I have added her to the appropriate groups via Active Directory yet when I try to add her to accepted users on the local machine she is taking over it can't find the user.  In fact, it can't add any legitimate user to remote desktop control on the particular client.  Any idea as to why this client wouldn't be able to find users to add to remote access permissions yet still have access to all domain shared resources?

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Have you tried clicking advanced from the screen that you enter the username on and ensure you are searching the proper "types" (ie Users or Groups) and from the proper location (ie: AD Domain)?
broadway69Author Commented:
Yes I have.  Users is selected and i have the domain selected.  Could this be tied to a service not running?
You can always try removing the machine from the domain and re-applying.  Not sure which service would cause this by the way.  Good luck.
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broadway69Author Commented:
When I'm trying to switch the location from the local machine to the domain, the pop-up window really drags as well.  Not as quick as when I try to add a network printer.  
Ensure your primary DNS server IP address is the IP address of the Domain Controller.
broadway69Author Commented:
Sorry for the long delay but yes.  The DNS is manually set to point to the domain controller.
broadway69Author Commented:
Problem was a corrupt Admin account which wasn't being given full access.  This took several weeks and many big brains at Microsoft to figure out.

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