Flash the Samsung firmware for your tablet via downloaded firmware from sammobile matching the model number and region of your tablet.

You need to do this with the tablet plugged in and booted to download mode. Instructions on how to do this are on every download page of every firmware on sammobile website.

This should fix your problem otherwise you need to do a factory reset probably.

How to flash Samsung Firmware: http://updato.com/how-to/how-to-install-...