Did anyone ever figure this out? If I flash the TWRP image manually with fastboot or use this Toolkit (which I donated to even though it hasn't ended up working) I just get stuck at the TWRP flash screen. I never get any menus to flash the TWRP zip or anything else. Used the toolkit to return to stock and start over. Manually returned to stock and started over. It makes no difference. Whatever I do I get stuck at the TWRP screen when I flash the temporary TWRP image. Can't get past it.
Did you used to be on the O beta? If so your partitions are messed up. You need to flash stock. The switch active partitions and flash stock again.