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First we can reset your iPhone and see if it works or not. Press and hold down the Power button and Home button at the same time until it shows the Apple logo. When you see the Apple logo, release the buttons and let it boot. Only reset if you know the passcode to unlock the screen of your device.
(If this is iPhone 7 or 7 Plus, then hold down Volume down and Power instead of Home and Power until it shows Apple logo)
Then check Maps. Please let me know if that didn't work, so we can continue troubleshooting.
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