As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AFTER DEPARTURE FLIGHT CREW SELECTED GEAR UP AND GOT ECAM MESSAGE NOSE WHEEL LANDING GEAR DOOR NOT CLOSED. FLIGHT CREW COMPLETED ECAM ACTION AND DOORS CLOSED. A LOUD POP WAS HEARD AFTER THE WHEELS RETRACTED PRIOR TO NOSE WHEEL DOOR CLOSING. MAINTENANCE REPLACED THE NOSE LANDING GEAR DOOR UPLOCK ASSMBLY PER AMM 32-32-14.