Try the following steps to fix the problem. After each step, check whether you are still having this problem.
- Simply double tap the icon of the app that you are unable to download and wait for a few seconds. Your download should resume.
- Tap Settings > General > Date and Time > Set Automatically > and slide to turn off “Set Automatically”. Manually set the date one year ahead. Now try to re-download the apps. If you get an error message, go back to turn on “Set Automatically” then try to download the apps again.
- Restart your iOS device. Simply press and hold the on/off (sleep/wake) button until you see the red slider and slide the slider to turn your device off. To turn back on, press and hold the on/off button until the Apple logo appears.
- Settings > iTunes & App Store > Your Apple ID > Sign Out. Restart your device, then Settings>iTunes & App Store>Sign in and then try again.
- Tap Settings > Wi-Fi and turn Wi-Fi off and then on again.
- Reset Network Settings by tapping Settings > General > Reset > Reset Network Settings, and then your iOS device will restart. Note that will reset all network settings including your Wi-Fi passwords.
- Reset your iOS device by pressing and holding the sleep/wake button and the Home button together until you see the Apple logo.