The emergency gear extension on the CRJs is accomplished by pulling on the emergency extension handle which is on the aft part of the central pedestal. Its position is such that it's rather awkward to pull from either pilot seat, so I was taught from my initial CRJ course that the PM should actually get up from his seat in order to pull on it. Once pulled, the handle will go through 4 "clicks", the first one being the nose doors opening, then one each for each gear leg. In addition to poor positioning, there is another "gotcha" in the system in that there is a button in the center of the handle in order to pull on the handle, and the button must be let go in order for the handle to stay extended, else it will try to restow. Once the handle is pulled, the mechanical uplocks release, the dump valves open, and the gear falls under their own weight. Read more here:
Bombardier CRJ 00 Landing Gear
If it didn't work, it maybe because:
1. The crew tried to pull the handle, but did it incorrectly, which is not hard to do due to the reasons described above.
2. The uplocks did not release or the dump valves did not open, which doesn't seem likely, but stranger things have happened...