You don’t really say much about what happened to the iPad '''''before''''' trying to revive it but this is a logic board related issue. Something is going on with the NAND, either it is not powered correctly or it is corrupted in some fashion. During the startup phase (or any Restore/Update action), the device goes through a self test of all subsystems and in your case, the NAND is not responding.
Tell us more about the history of the device and we may have a more precise diagnostic but this will likely not be a DIY repair