Hum nobody answer?? does this mean nobody knows how to use the dive comp?
Toodus i dont have a D4 but i often saw my buddies adjusting to Dive Air before they enter the water.
They always alert this ritual before their 1st initial dives or pre-check.
They did not have to adjust the mode after that 1st dive.
Other wise it will just act like a gauge and a timer.
I think in your case, you may have skip that 1st part and so it lock to free mode until finish the no fly time.
In the manual it said that you able to change from free mode to dive air provided you were doing the free dive in the 1st dive.
In free diving no one can hold a breath up to 10min.