Although your iOS 8.1 device -- such as an iPhone or iPad -- has built-in apps that you can use right out of the box, the App Store has over one million more apps that can further extend your device's functionality. You can usually access the App Store from your iOS device over a cellular data connection -- on a cellular-enabled iOS device -- or Wi-Fi. When your device cannot access the App Store, it displays a pop-up alert displaying information you can use to resolve the problem. In some cases, you may also need to perform other troubleshooting steps to reestablish a connection to the App Store, such as updating your device, checking your Apple ID credentials and performing a reset.
Troubleshoot the Internet Connection
Without an active connection to the Internet, your iOS device displays an alert -- such as "Cellular Data is Turned Off" -- when you attempt to connect to the App Store. The reason that your device cannot connect to the Internet may be the result of an external factor, such as unusually low Wi-Fi signal strength, or a change in your device's settings -- such as the activation of the Airplane mode. Move your device closer to your Wi-Fi router if you have a low or intermittent signal. If your device is cellular-enabled and you don't have access to a Wi-Fi network, activate the cellular data option in the Cellular section of the Settings menu. You can check the status of your device's Wi-Fi adapter and Airplane mode feature by launching the Control Center, accessed by swiping your finger up from the bottom of the device's screen. If applicable, disable the Airplane mode feature and activate the Wi-Fi adapter.
Review Your Apple ID Information
Your device may not be able to access the App Store if you accidentally entered the wrong Apple ID and password to connect to the digital download platform. For example, you may have an Apple ID for the App Store and a separate ID for iCloud services. Tap the "Settings" icon from the Home screen, select "iTunes and App Store" and then check the displayed Apple ID. If it is incorrect, tap the ID and select "Sign Out." Enter the correct Apple ID login information and tap "Sign In." To view the details of your Apple ID, tap the ID and select "View Apple ID." Enter your Apple ID password to open the Account Settings screen. Important data about your Apple ID is displayed on this screen, such as your payment information.
Update the Date and Time
It is essential that your iOS device's date and time settings are updated and accurate because the App Store uses the settings to authenticate the connection to your device. Tap the "Settings" icon from the device's Home screen, select "General" and then tap "Date and Time." Review the Time Zone section for accuracy. If the information is incorrect, tap "Time Zone" and then enter the correct time zone for your location. You can also manually set the correct time by tapping the current date and time. If the date and time setting is correct, slide the "Set Automatically" switch to the "On" position. If your device is cellular-enabled, such as an iPhone, it automatically acquires the correct time over your cellular network. If the device is not cellular-enabled, it accesses the updated time over your Wi-Fi network.
Perform an iOS Update
Your device may have a problem connecting to the App Store because it is not running the latest version of iOS. Like other operating systems, iOS is also susceptible to glitches and bugs that can affect your device negatively, such as an App Store connection problem. Keeping iOS on your device current can address problems that prevent a connection to the App Store. Tap the "Settings" icon from the Home screen, tap "General" and then select "Software Update." Any available updates appear on the Software Update screen. As a precaution, back up your device before updating iOS to avoid losing data. If your device is having difficulties updating wirelessly, you can complete the update process on your computer using iTunes.
Reboot Your iOS Device
In some instances, a simple reboot of your iOS device can stop any active processes that are preventing access to the App Store. The first way to perform a reboot is to restart your device. The initial part of the restart process completely powers down your device. After the device has turned off, you have to press the "Sleep/Wake" button until the Apple logo appears to turn it back on. The second method is to perform a reset, which turns your device off and then automatically turns it back on. The difference between the restarting and resetting process is that the reset process forces your device to restart if it is unresponsive.
Although you can access the App Store on a cellular network with a cellular-enabled iOS device, you cannot download an app over a cellular network that is greater than 100MB in size. The 100MB limit is set by Apple and not your wireless company. If you want to download any app over the 100MB limit, you have to wait until you can connect to a Wi-Fi network.