We have seen how you can add more features to Windows 8.1. But there may be times that this procedure may not work. Let us say that to upgrade your Windows 8 edition to a higher edition you open Control Panel > System Properties and click on Get more features with a new edition of Windows. You then buy a key and enter it via Add features to Windows 8 link.
Cannot add features to Windows 8.1
Normally in such a scenario, your Windows 8 should upgrade to a higher edition. But in rare situations, you may find that the feature does not get added but instead a system restore operation starts, and your Windows returns to the previous state.
In such a case you can find if a service called NLS Service is present on your computer.
To do so, open the Win+X menu, type services.msc and hit Enter to open Services. Here check if you can find NLS Service. The NLS Service runs nlssrv32.exe and is part of Nalpeiron License Management. This service enables products that use the Nalpeiron Licensing System.
The nlssrv32.exe is typically located in the C:\Windows\System32\ folder and used by many software developers including NitroPDF, Alien Skin, Altiris, BCL, Symantec, etc. If you have installed any of their products on your system, in all likelihood, this process will be present on your PC.
KB2787752 says that this service is known to interfere with the upgrade process. So if you find the NLS Service, change its start-up type to Disabled and restart the computer.
Once you have done this, try to add new features to Windows 8. It should help.
Do remember that to add features to Windows 8, your PC must be running an activated copy of Windows 8.