"To go below a minimum numeric requirement": opposite of "exceed"
Solution 1:
For an error message, one might
- fall short of
- not reach/attain
- fail to reach
- fall below
a minimum value.
For a single word, you could say the minimum value is unattained, but that's an awkward way of putting things.
Solution 2:
You could use undershoot or under deliver.
Solution 3:
The term underrange is apparently used. Its obverse is overrange.
It doesn't appear to be very common though.