RDS Licensing

I tried to add CALS to my RDS License Server on the web site of activate.microsoft.com, but failed, it mentioned:

Remote Desktop Services Licensing is unable to process your request. Make sure you provided correct information. If the problem persists, try other methods of activation. Error code is 800.

My Product ID is : 00184-30000-00001-AT420

Windows Version is : Microsoft Windows Server 2012 Standard

I verified all of the information was correct.  This was the third server I activated and tried to put cals on, but this was the first one to fail.  We should have plenty of CALS left.

Thanks,

Tom