I sent an email to the folks at Makerbase, who provide the motherboard that the Sapphire uses, and they confirmed that if you use what they call the "double z", that is, 2 z-axis limit switches, you can't use the BLTouch. Now, I vaguely remember reading somewhere that there might be more flexibility if you swap out the firmware with a different piece of software, "Marlin", maybe, but that might have been just been conjecture.

For now, I'm going to recheck the connections, as Rury suggested, and then maybe spend some time browsing the menu items while I wait for the replacement parts to arrive. Still a lot to figure out, at least for me to understand it better.

Thanks again for your help.