QGROUNDCONTROL altitude error

I’m using QGroundControl for ground station and I’m not getting an accurate altitude reading, It may show negative number like -2.4 and not make any changes , when the quad is 80 feet off the ground,
Not sure what to check and where to find the settings to make the changes,
It was working fine Before , so not sure what I did for this to happen,
Thanks for any help

Try to reset and reload firmware onto your Cube. This usually solve most of the software problems.

If the problem is still there, check if the barometers are working, from the live tuning screen in Mission Planner.