I am writing this here from my personal experience. After completing a fresh windows 2008 R2 Web edition on my server. I have experienced the same issue.



Reason and Solution

This software is for evaluation and testing purposes. Evaluating any version of Windows Server 2008 R2 software does not require entering a product key, however will require activation within 10 days. Failing to activate the evaluation will cause the licensing service to shut the machine down every hour (The 10 day activation period can be reset five (5) times by using the rearm command. See below for further information on activation rearm).  After this time, you will need to uninstall the evaluation software and reinstall a fully-licensed version of Window Server 2008 R2.

 

Follow these steps:

Open Windows PowerShell

To check current license status, run slmgr -dlv

To ream Windows license, run slmgr -rearm.

Restart Windows, run Restart-Computer