On a lot of the lenovo tablets and phones there is a reset button in the SD card slot you will need to reset it. Not sure on your model but its worth a look . If theres not one then try removing the battery then leave it sit for an hour and then put the battery back in and reboot the phone . While you have the battery out it wouldnt hurt to check the battery with a multi meter against the power out specs listed on the battery. Hope this helps