Parameter issue on MAVlink Inspector in QGC


Hello, I’m in trouble with parameter issue about altitude. I want to know why parameter ‘altitude_terrain’ and ‘bottom_clearance’ is ‘nan’.
I think that barometer is inaccurate and range sensor may not connect even It certain work. And I tried to change parameter ‘MPC_ALT_MODE’ to 'terrain following. Despite some trying. it doesn’t fix. I need your help.