Questions about Uniden scanners can generally be put here - we have separate forums for each state as well as programming software.
Just because it covers that frequency range doesn't mean that it will trunk in them. At the time this radio came out, trunking as an industry was just getting more or less off the ground, and UHF trunking simply didn't exist in many places as yet. So the necessary instructions for the firmware on the scanner couldn't be developed.
Happily there are many 2nd generation and later trunktrackers that will handle this mode now, but nothing back as early as that 235
HTH...Mike