Open your GR8 and look for a battery cell. Extract it, press and hold on the power button pushed to get rid from any static electricity in the motherboard. As the RAM, the CMOS is based on a volatile memory which can't subsists without any power.
Once you'll reboot the computer, you will have to go to UEFI to rectify the nullified date settings (brought back to it original state out of the factory), and then, try to reboot. By the way, update your UEFI if not done.
In the attached thread from one of our member, you'll find a video explaining how to do this from a G20, it should be similar. (
https://www.youtube.com/watch?v=soWlrkA12wY)
PS: Can you at least boot on UEFI settings without any drive? If you can't, check every connections once again (specially your DRAM and your processor) and your power supply. If you find nothing, you're in trouble..