Make sure you're connected to Wi-Fi
You can only download apps up to 150 MB in size without Wi-Fi. You can also try going on the Internet to check your connection.
If you’re using cellular data or Wi-Fi and have issues with an app, try to connect to another Wi-Fi network. You can use cellular data for apps up to 150 MB* in size.
To check your Wi-Fi connection, try streaming a video from the Internet to see if it loads quickly. Get help connecting to Wi-Fi or contact your Internet provider for more help.
Pause and restart the app download
Try stopping and restarting the download.
See: How can I cancel an app installation on the iPhone?
- Pause the download on the iPhone by tapping the icon.
- Connect the iPhone to iTunes. This will cause iTunes to start downloading the app.
- Go to the Downloads tab in iTunes and delete the download.
You can also restart your device.