Ring Intercom with Bell System 801 P16-160 error

Hi, I've had Ring Intercom a couple of months and it was working fine as expected. I upgraded my handset to a Bell System 801 because the existing handset had a ridiculously loud buzzer. But now when I try and connect the Ring Intercom, it does not detect the buzzer during setup with a P16-160 error code. I have: - Checked/redone the wiring several times - Factory reset the intercom and gone through the process - Checked wifi connection etc Setup as follows: - C2 into port T - C3 into port R - C4 into port O - C5 into port Z - C6 into port I Everything on the handset works fine (mic, speaker, buzz, unlock). I was also able to unlock using Ring app before I factory reset the Intercom, which I can't do even do that now because I can't get past the setup screen.