I went back in and reseated the trackpad ribbon cable and reclosed the ZIF connector, which restored the keyboard. I used an external monitor to confirm that the laptop is booting up. I also reseated the display cable, but that did not work. I have a new cable coming in a few days, and I’ll replace the current cable, hopefully to fix the issue…

After performing the steps, and the low power startup procedure, on initial startup I had chime, the battery charging image (48%) and then the screen went gray - and the mouse pointer was on the screen and it would respond to the trackpad. Then the screen went squirelly (kinda like it lost sync). I restarted the laptop and then the screen went blank. I’ve gone back in a couple of times to reseat the display cable, to no avail. And I’ve lost the keyboard lights. So I’m going to take a breather and try to perform steps 1 to 22 over again. Any advice?