This post wants to help you out when you would like to update to Windows 8.1 via Windows store but failed. It’s said that some people could not find Windows 8.1 update in Windows Store- Windows 8.1 are not available in Store.
But why do this happen? This is because you PC has not installed the “KB2871839” update and consequently you have trouble getting the Windows 8.1 update notification through App Store.
To solve the problem, press Windows logo key and C key together on the keyboard or swipe inside from the right screen edge -> Settings -> Change PC settings -> Windows Updates -> tap or click on Install. (see screenshot below)
Once you complete the steps above, open Windows Store and try again. Generally, you will see the Windows 8.1 update notification once the APP Store is open.
If you could not download the update from Windows updates, you can download KB2871839 from Microsoft.com manually. To download KB2871839 by hand, click the link:
->Choose 32-bit version or 64-bit according to your current Windows. (see screenshot below)