Hello SrinivasanAG,
thank you for posting on the Microsoft Community Forums.
To resolve this issue, firstly, double-check that the product key is correct and that your server is connected to the internet. If these have no problem, Windows has a built-in troubleshooter that can help resolve activation issues. Go to Settings > Update & Security > Activation and run the troubleshooter.
Additionally, you can try a phone activation:
- Open the Command Prompt as an administrator.
- Type "slui 4" (without quotes) and press Enter.
- Select your country or region from the list and click Next.
- Call the telephone number provided and follow the instructions.
Best regards,
Lei