Hello, I have the same problem, I just sent a message to Asus reporting the problem:
"When I install a new NVMe SSD (1TB WD BLUE SN550) in the second slot, the BIOS doesn't detect it, neither does Windows. Also when trying to move your original SSD from the laptop from the first slot to the second slot, you don't recognize it either. It seems as if it is disabled, I expect some quick solution. "
PS: The 1TB WD memory is recognizable in the first slot.
Can the problem be caused by 32GB of optane memory?
Or maybe only the second slot is disabled and there is a solution if they upload a new update to the bios or the socket is broken.