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It might be a problem on Google's end. However, sometimes, resetting app preferences might help. Settings>Apps>Menu>reset app preferences.
Welcome to Android Central! Does it still happen after rebooting the phone? If that doesn't help, try going to Settings>Apps>All, select Google Play Store, and Clear Cache.
And if even that doesn't work, sometimes removing the google account in the phone and adding it back fixes things. (I'd restart the phone between removing and adding.)