Hello future Googlers! I managed to figure this out as the previous suggestions posted did not work for my tablet (thinkpad tablet 2 Compliance ID: TP00043A)
What I did was (using the original AC adapter and usb cable plugged in to power):
plug in the power
using a straightened paper clip, insert it into the hole on the bottom edge of the tablet to the left of the docking port until you feel it click
hold for 20 seconds
remove clip
unplug power cable
insert clip again and hold for 20 seconds
plug power back in
press top power button
hope this helps!