If your Modern or Metro apps will not start or fail to start in Windows 8 | 8.1, then it is quite possible that the default registry or file permissions may have been modified or corrupted.

Clicking on the tile of a Modern app will begin to launch the application but the app simply returns the user to the start screen.

To resolve this issue, the Registry and File System permission must be reverted back to a state that will allow modern applications to function.

For more details on ho to do it, visit KB2798317.