As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LANDING GEAR HANDLE PUT IN GEAR DOWN, LANDING GEAR DID NOT MOVE. GEAR DISAGREE RED MASTER WARNING. WRC/QRH CYCLED GEAR WITH NO CHANGE. PERFORMED MANUAL GEAR EXTENSION / REMOVED AND REPLACED LANDING GEAR SELECTOR VALVE IAW CRJ AMM 32-32-10-000/400-801. ALL OPS CHECK GOOD.