Onboard mag calibration not starting

ArduPlane Plane 4.5
1

My compass is not working - randomly shows any heading in Mission Planner.

When I click on Onboard mag calibration absolutely nothing happens.

Any ideas?

Thanks

2

Is it recognized on the HW ID screen?

3

Yes, 2 compasses show. I guess the Pixhawk onboard and the external one.

4

Be sure that both compasses are “USED”, otherwise MissionPlanner does nothing.

EDIT:
Another thing, you need a GPS 3D Fix, otherwise MissionPlanner also complains.