Like Play Store for Android or iTunes Store for iOS and Mac, Windows Store for Windows 8 is also growing with new apps and games each day. However, it is not possible for everyone to find and install every app available on Windows Store. If you are unable to find or install an app from the Windows app store, it might be due to any of the 7 reasons mentioned below.
1. It might be due to your preferences settings that hides apps. Apps that don’t meet your preferences are hidden when you browse or search the Store. Set your preferences for the Windows Store to see and install apps.
2. Family Safety settings might be hiding apps because of age rating. Using Family Safety settings with the Windows Store, you can prevent children from installing apps that are inappropriate for their age. Change settings if you want to install a particular app.
3. Not all apps are available in every country or region. Although an app might be available in several different countries or regions, the developer might have decided not to release it in your country or region.
4. The payment method associated with your account isn’t from the country or region you’re in. To buy an app from the Store in a specific country or region, change your home location.
5. For some reason the app is no longer available in the Store. Though, you can see the app description page on the web, but you can’t view the app in the Windows Store, instead you’ll see a message that the app isn’t available.
6. Your PC’s processor is incompatible with the app. The Store automatically hides apps that are incompatible with your PC’s processor so you don’t install apps that won’t run on your PC.
7. Your PC doesn’t meet the system requirements for the app. You won’t be able to install an app if your PC doesn’t meet the system requirements for it. If your PC meets the system requirements for an app, but you’re unable to install it, check to make sure you’re not signed in to the PC or the Store using a temporary or guest account. [Source]