Fish and wildlife are now utilizing P25 Phase 2 mode. They also used to simulcast across all towers, whether a unit was affiliated to the specific tower or not. There was a change in the past few months where fish and wildlife units now only broadcast on the towers that the radio is affiliated to,and no longer simulcast across all towers at the same time as state park police currently do. Fish and wildlife also have a few encrypted talkgroups as well, and the database is correct.
You failed to mention which site(s) you're scanning, however the bottom line is that if no subscriber radios are affiliated with any of the sites you're scanning, the talkgroup won't be active at those sites, and you won't hear any activity.