Terminal Services server issues temporary licenses to all the client machines connecting to terminal services. It is required for the terminal services to process the request in timely fashion and will generate the hardware ID to keep the licensing information for client machine. This hardware ID is stored on client machine. This hardware ID is used to check the expiry of license. If license is expired terminal services server can not re-issue license to same computer account. Generally all the temporary license are valid till 90 days.

There are two ways to get rid of this when a client machine needs to have access to Terminal Services session but its license has expired:

Change the computer name.
Remove the License key from client computer.
The second method is very useful. It just requires a registry setting to be removed from client computer. The following registry settings must be removed from client computer:

HKLM\Software\Microsoft\MSLicensing
HardwareID
Store
LICENSxxxx

After deleting above sub-keys try connecting to your Terminal Services server you should be able to get in.