Bad Compass Health message but no compass installed

Thanks in advance for any help.
APM 3.1 board, Ver 3.2.1 firmware, Helicopter setup, 450 Pro heli, Tarot FBL head.
This setup was working well for a few weeks while in the process of trying to tune the heli. Problem started for no reason I know of, I am getting a BAD COMPASS HEALTH message when trying to arm, thing is I have no compass hooked up, never did have? In mission planner mandatory hardware, compass, I have no boxes checked, nothing to indicate I have a compass installed?
I have read a lot of topics pertaining to bad compass health but these are people with a compass hooked up, I have none?
Any ideas to why I have this problem or is there a know fix for this?