How to fix "App not installed"? I have Galaxy S4 GT-I9500, plus I have much free space. Some apps have trouble to be installed which end after pressing "Install" and telling me "App not installed".

Please I need a solution for this weird issue.
This means the SD card hasn't been fully checked and mounted, and the app you're trying to run is on the SD. That's why you see the icon, but can't run it for awhile.