iPad Pro 5th Generation won't boot black screen, limited amperage draw

The iPad suffered impact that shattered screen. The amperage draw is continually .48, far below normal, regardless of how long it has been left on the charger. The charging port has been replaced and tested with no change. The screen has been replaced as well. The screen is black and there is no evidence it ever boots. Have tried soft reset (vol up, vol down, power). No change. New MFI cables and chargers have been tried. It will not mount for wipe/restore. Does not appear visible to external devices.