The issue has been resolved .
Below are the steps that I followed :
- Fetched the KMS client key for Windows Server 2025 x64 Standard Link : https://learn.microsoft.com/en-us/windows-server/get-started/kms-client-activation-keys?tabs=server2025%2Cwindows1110ltsc%2Cversion1803%2Cwindows81
- Open command prompt(or powershell) as an administrator.And run the below command.
dism.exe /online /Set-Edition:ServerStandard /ProductKey:xxxxx-xxxxx-xxxxx-xxxxx-xxxxx /AcceptEula
Note : The product key is to be fetched from step 1.
3.The server will ask for a reboot. Reboot the server.
- Last step , now here you need to enter the KMS key you or your customer has given it you for activation.
Go to Settings -> System ->Activation->Change Product Key