At this point on reassembly, make sure the optical drive SATA cable is under the black plastic wall prong. The connector must be low to reach the optical drive.

This was my only error on reassembly. The SATA cable must be under the black plastic prong. I did not want to pull to logic board again. I managed to bend the black plastic bits and get the cable in the right place.

I think my cables were in the opposite order—but I put them in the instruction order and everything is working.