GE Simon V2 - Add/Delete Sensor "FUNCTION NOT AVAILABLE"

I have a sensor that has gone bad, but am unable to delete it because the unit says “FUNCTION NOT AVAILABLE”. I have a new sensor that I bought https://www.valinonline.com/products/1082-n , but the ADD function is also not available. I have what I think is the “MASTER ACCESS CODE”. I have scoured the manual, but can’t find the “secret”. Anyone know it?