I put it together carefully and with care but for some reason it wouldn’t turn on.
verify that your Micro-SD card is inserted correctly. Try pressing the reset button on the opposite side of the logic board from the power button. The GameShell should turn on as soon as the USB power source is connected.
Failing the above, try removing your Micro-SD card and try mounting it on your computer. This can be with a USB Card Reader or with an SD card adapter in the computer’s SD Card slot if you have one. It should mount, at the very least a boot partition. If it doesn’t, try following instructions elsewhere in this forum to write a new image to the card.