Why can't I find the Win8.1 update in the Win8 app store?

        Microsoft will push Windows 8.1 updates to Win8 users for free through the Windows Store app store at 19:00 tonight, but some users will ask why I can't find Win8.1 updates in the app store. Take a look at Microsoft's official answer:

If your computer is currently running Windows 8 (or Windows RT) and you want to update to Windows 8.1 (or Windows RT 8.1), in most cases you will be on Windows See the free updates in the prominent location of the app store homepage. If the app store is open but you don't see the update, it may be caused by one of the following reasons:
1. You may need the latest updates from Windows Updates
Although you have downloaded and installed the Windows 8.1 update from the app store, you The computer also needs another update, "KB KB 2871389", and the app store will provide you with Windows 8.1.
If you use Windows Update to get automatic updates, KB 2871389 will be downloaded and installed automatically.
If you have turned off automatic updates, or if you use a new computer that has not yet downloaded automatic updates, or if you don't want to wait for Windows updates to do this automatically, you can go to Windows Update and manually install KB 2871389.
1, steps to install the required updates
1 Open Windows Update by following the steps below: Swipe in from the right edge of the screen (or, if you are using a mouse, point to the lower right corner of the screen, then the mouse pointer Move up), tap or click Settings, Change PC Settings, and Update & Restore.
2 Click or click "Check Now" and wait for Windows to find the latest updates for your computer.
3 If you find an update, tap or click View Details.
4 In the list of available updates, select "KB 2871389" and any other updates you want to install, then click or click "Install".
5 Read and accept the license terms, then click or click Finish (if the selected update requires this).
2. Note
• It may be necessary to restart your computer to complete the installation of some updates. Please save and close all files and apps before restarting to avoid losing any data.
After installing KB 2871389 and restarting your computer, go to the Start screen, tap or click App Store, and look for the Windows 8.1 update.
Second, the Windows 8 version you are running may not support free updates from the app store.
Some versions of Windows 8 do not support free updates to Windows 8.1. These versions include:
• Windows 8 Enterprise Edition
• Enterprise Windows Professional Edition with KMS Activation installed
• Windows 8 version installed with MSDN ISO and activated with Volume Activation Key
If running One of these versions is not available for free updates from the app store to Windows 8.1 or Windows RT 8.1.
If you install Windows 8 using MSDN ISO, you may be able to install Windows 8.1 using a similar ISO in MSDN. Otherwise, you can perform a fresh installation.