Like a car battery, if the Trofa's Nexus tablet fully drains, it will need a jump start.
To jump start it, first open the door to the machine and locate the nuts which hold the tablet to the retaining bracket. Unscrew these to remove the tablet, disconnecting the USB cable from it after the bracket has been removed. If using a nut-driver tool, the nuts are 7mm.
Connect the tablet to a USB wall-charger. Then, place it into bootloader mode by holding down the power and volume-down buttons simultaneously until it boots to this screen. Then, leave it charging overnight.