Uncheck the depth fence option, and you should be good to go.
I just fixed a bug in QGroundControl this morning where the Max depth value in that field was not set correctly, your maximum depth was probably set to the default of 10 meters.
If you do want to set the maximum depth in software set the following parameters:
FENCE_ENABLE: Enabled
FENCE_TYPE: Altitude
FENCE_ACTION: Warn Only
FENCE_ALT_MIN: -100m or whatever limit you want
FENCE_MARGIN: 0, or added buffer to stay away from limit
Note that the limit is only enforced in depth hold mode.