As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, THE CREW RECEIVED A (GEAR UP DISAGREE) MESSAGE. THE QRH WAS COMPLIED WITH, AND EMERGENCY DECLARED AND THE AIRCRAFT RETURNED TO DEPARTURE, LANDING SAFELY. MAINTENANCE ADJUSTED THE UPLOCK PROXIMITY TARGET ON THE LEFT MAIN LANDING GEAR (MLG). OPERATIONAL CHECKS GOOD. AIRCRAFT OK FOR SERVICE. (K)