The update does not show up in the Windows Store, some complain
Microsoft announced not a long time ago that its new Windows 8.1 is available for download, but plenty of users complain that the update is not yet displayed in the Windows Store.While Windows 8.1 should be there for most people, one of the reasons while you can’t see it right now is that Microsoft is releasing it gradually across the world, in an attempt to make the updating process as smooth as possible.
We’ve heard that Redmond estimates that the global rollout could take even 30 days, so in some cases, you might have to wait up to one month to be able to get your hands on Windows 8.1.
Once it becomes available, simply launch the Windows Store and click on the Windows 8.1 logo, as the updating process is fully automated and no user input is required.
Update: if you can see the update in the Windows Store, here's you can download Windows 8.1.