Touch ID Not Working
Touch ID is a very convenient feature, as it lets you authorize app purchases by simply scanning your finger instead of having to enter in your Apple ID password every time. However, sometimes it doesn't work in the App Store.
To fix an unresponsive Touch ID, go to Settings > Touch ID & Passcode and turn off iTunes & App Store. Restart your iPhone and go back into Touch ID & Passcode in Settings. Turn back on iTunes & App Store.