Welcome to Android Central! Are you able to power down the tablet by pressing and holding the Power button for around 10 seconds? If so, try booting into Recovery as follows:
1. Press and hold Power until the device powers on, then immediately press and hold Volume Down (while still pressing Power). You will see the word Start with an arrow drawn around it.
2. Press Volume Down twice to designate Recovery mode.
3. Press Power to restart into Recovery mode. You will see an image of an Android robot with a red exclamation mark.
4. While holding down Power, press Volume Up, then release. You should now see the Recover Menu.
5. Use the Volume buttons to highlight "Wipe cache partition." Press Power to execute. This will not erase anything important--only system log files and temporary data.
6. When finished, press Power again to select "Reboot system now." Does it work?