I cannot tutor You what to do but i can suggest You to try this way, other than this i wouldn't have idea how to fix it, please keep that in mind...
Those are steps:
Turn off device...
Than press the Power and the Volume Up button together (if not working try Volume down button) till the device displays the start-up logo than release the buttons and wait till the device enters the recovery mode, than use Volume buttons to move up/down and find "wipe data/factory reset option", once the option is highlighted, press the Power button to select the option.
On the next screen, press the Volume Down button multiple times till the Yes -- delete all user data option is highlighted.
Press the Power button to reset device.
I hope this was helpful to You, if that's not the case good luck finding the answer.