If you encountered this situation, it means the tablet is locked and there is no way to unlock it unless you perform a factory reset. Look on its margins for a small hole and use a sharp pin to press the button while the tablet is on. This should reset it and then you should have access to it. Alternatively, press Volume Up + Power until the Android recovery appears. Select Wipe data/Factory Reset and then confirm the select with Power button. Reboot it and you now should have access to tablet.