Recently I have faced a Problem that all of the Windows Server 2003 Clients cannot Remote Desktop to Windows server 2012 Session host server. They have prompted with following error.
“The remote session was disconnected because the remote computer received an invalid licensing message from this computer”
I have two Windows server 2012 session host servers and this issue only occur to one of the servers. I have tried to solve this by adding different settings that have suggested in blogs and articles but nothing helps. After getting Microsoft support, they have suggest a solution that helps to resolve the issue.
Please use following steps to resolve this issue.
- Login to the Session Host server (Server 2012)
- Backup the registry
- Find the following registry key
“HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TerminalServer\RCM” - Delete following registry keys
- X509 Certificate
- X509 Certificate ID
- X509 Certificate2
5. Restart the server
If the issue is on this, deleting these registry entries will make windows server 2003 clients successfully login to windows server 2012 session hosts.
Hope this information is useful.
Asitha's Blog 
HI Asitha,
Above information is very helpfull. After I deleted the registry keys it worked fine for first time RDP from 2003 server but after first time the reg keys are reproduced automatically, which is again throwing same error. Could you please help me to solve this.
Hi Arun
I faced the same issue with some of 2012 RDSH servers, but not all of it. i escalate it to Microsoft and their recommendation is to re-install the license server but they are also not sure it will fix the problem. so i didn’t go for it. just do the registry delete for two three times and restart. it will help you for some time. but eventually you have to replace 2003 servers because its been end of life. i’m doing same with my setup.