As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON FINAL APPROACH THE CA REPORTED THE GEAR DID NOT COME DOWN AND THEY RECEIVED A GEAR DISAGREE MESSAGE. RECYCLED LANDING GEAR SELECTOR AND NO GEAR EXTENSION. CREW PERFORMED GO AROUND AND FOLLOWED QRH. GEAR EXTENDED WITH EMERGENCY LEVER. EMERGENCY DECLARED. AIRCRAFT LANDED WITHOUT INCIDENT AND WAS TOWED TO THE GATE. MAINTENANCE REPLACED LANDING GEAR SELECTOR VALVE (TC# 20190430002)