I have a tablet with 8.1 with bing. I want to upgrade it to 8.1 Pro so I have an OEM windows 8.1 pro license (unused) . When I go through the install another version of windows it says Key checks out and installs added features of 8.1 pro. When I go to activate. It says its unable to activate the product key dosen't work inform store or company or I can buy a new one from windows. Is it a bad key or oem licenses are unable to be used for upgrade???