When downloading, updating or syncing apps to an iDevice, apps may occasionally get stuck waiting and never install on the device.
First, give the app enough time to download and make sure it’s actually stuck before proceeding. Most apps download within a few minutes over Wi-Fi but if you are downloading or updating several apps this could take much longer depending on the size of apps and the speed of your internet connection.
Also, if you are downloading or updating apps over Wi-Fi or 3G make sure the problem is not with your data connection before proceeding.
Restarting iOS Devices
The easiest way to clear up apps that are stuck waiting is a Restart.
To Restart or Reboot your iPad, iPhone or iPad touch;
This will sometimes clear up apps that have difficulty installing but if that did not resolve your problem then keep reading.
Download and Sync Apps With iTunes
If you were installing a new app that is not on your computer, you should be able to download the app without being charged. Make sure you are signed in with the same account that made the purchase. When you locate the app in the iTunes Store, you should see “install” or “Downloaded” instead of a price. Download the app or apps to iTunes on your computer.
Remove and Reinstall Apps
Hopefully your problem has already been resolved by this point but here’s one more method that should certainly clear up the issue. I have saved this for last since it is the most time consuming. The length of time will depend on the number of apps you sync to the device.