Here are three ways to try and get the scanning working again.
Option 1 ... Check inside to make sure you didn't dent, knock loose, etc., anything when you replaced the battery.
Option 2 ... Clear cached data in the Fingerprints app. Go to "Settings" and then select "Application Manager". Now go to the "All" tab, then tap the entry labeled "Fingerprints".
Option 3 ... Hard reset the device. This one you don't want to do unles you truly have no other options. Why? Well, it will erase all personal data and reset the tablet.
NOTE: Doing this will clear 'all' the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the device.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the tablet...
1. Make sure that the tablet is actually powered off.
2. Press the "Power" and the "Volume Up" buttons, together, until you see the start-up logo on the screen.
3. Once you can see the logo, release the buttons and allow the device to enter the "System Recovery Mode".
4. Next use "Volume Down" button to get to the "wipe data/factory reset" option When in recovery mode the "Volume Up" and "Volume Down" buttons are how to can navigate and highlight what option you need.
5. Once you have selected the "wipe data/factory reset", press the "Power" button to select that option.
6. On the following screen, repeatedly press the "Volume Down" button until the "Yes - delete all user data" option is what is selected.
7. Then press the "Power" button to hard reset the tablet.
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