Thanks, everyone, for trying to help! Mitz was able to get in touch with me and walk me through some troubleshooting. Since the machine was new to me, everything had been taken apart—including the sensor arms (not sure if that’s the correct name) that seat into the sensor housing. Once those were reinstalled, it homed just fine Thanks again, everyone—especially Mitz—for taking time out of his schedule to help out a stranger.