Lidar STVL53L1X Holybro is not working Automission

Issue details

I am using Lidar ST VL53L1X from holybro with ardupilot firmware; this lidar is set facing down detecting altitude.
When using it with automission plan mode, lidar is not working, i mean it doesnt react when detecting low ground level.(mission plan is at 4m altitude in all waypoints but 1 waypoint got much higher ground level in which the drone should automatically up to maintain the 4m altitude). Please help on how to fix this.
Also please let me know what is the best rangefinder with ardupilot firmware in auto mission mode.

Platform

Copter

Airframe type

_Quadcopter

Hardware type

_Pixhawk Px6c

Mission planner version

1.3.81 build 1.3.8741.25556

Ardupilot firmware
V4.5.2