As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAKEOFF THE MAIN LANDING GEAR (BOTH LEFT AND RIGHT) WOULD NOT RETRACT. CONTINUALLY SAW GREEN DOWN INDICATORS AND GEAR DISAGREE. THE NOSE GEAR CAME UP NORMALLY. REMOVED AND REPLACED MLG SELECTOR VALVE IAW CRJ-900 AMM 32-32-10. OPS CHECKS GOOD IAW CRJ900 32-30-00. P/N ON/OFF 53340-7, S/N OFF NGL/1590/07. MXC NOTIFIED.