Windows can present an error during activation for many different reasons, please run through the troubleshooting steps in the order listed below.

1. Internet Connection & System Time

   Make sure your computer is connected to the internet and that the system date and time is set correctly for your local timezone.
   
   

2. Activation Troubleshooter

   Run the Windows Activation Troubleshooter which will attempt to automatically resolve any issues.
   
   

3. Windows Update

   Check Windows Update for any outstanding updates, download and install any outstanding updates.
   
   

4. Restart

   Restart your computer and retry the activation.
   
   

5. Phone Activation

   You may be given the option to use the toll-free phone activation service, do this by clicking the Activate by Phone link on the activation page.