As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD INFLIGHT T755/05DEC - NOSE LANDING GEAR WOULD NOT RETRACT AFTER TAKEOFF. RETURNED TO ORD AND LANDED WITHOUT INCIDENT. ACCOMPLISHED NOSE STRUT REPACK AND REPLACED SCHRADER VALVE AND SERVICED WITH DRY NITROGEN. SYSTEM GROUND CHECKED NORMAL OPERATION.