I am using windows 8 pro edition on my system but I am unable to update windows 8 to windows 8.1.

I am using Volume License key MAC/KMS. so plz tell me that how to update windows 8 to windows 8.1.

You need to contact the source of your VLK.  If you are not in an enterprise situation you may not be able to upgrade with a volume key that cannot contact a KMS server.

How to contact the source of my VLK. I am using windows 8 Pro VLK.

Where did you get the volume key?

If you are not in a corporate environment the key is probably not legitimate.

Hi,

As mentioned by MVP ZigZag If you are in organization or institution and using Volume license legally

Cantact with Microsoft Volume Licensing Service Center

https://www.microsoft.com/Licensing/servicecenter/Help/Contact.aspx

Regards,

D. Wu