As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WOULD NOT PRESSURIZE AFTER TAKEOFF. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND AIR CYCLE MACHINE DISCHARGE DUCT DISCONNECTED. REPOSITIONED DUCTING AND SECURED ALL CLAMPS. LEAK AND OPERATIONAL CHECK NORMAL.