As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE RED NOSE GEAR LIGHT REMAINED ILLUMINATED WHEN GEAR WAS RETRACTED AFTER TAKEOFF. THE GEAR WAS CYCLED, BUT THE LIGHT REMAINED ILLUMINATED. THE AIRCRAFT WAS RETURNED TO DEN WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE NOSE GEAR UPLOCK PROXIMITY SWITCH OUT OF RIG. THE PROXIMITY SWITCH WAS ADJUSTED IAW MM 32-60-05. IN ADDITION, THE NOSE STRUT WAS SERVICED WITH NITROGEN. A NOSE GEAR SWING WAS PERFORMED WITH OPERATION AND INDICATIONS CHECKING NORMAL.