As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB DTW-ORD, FOUND THAT THE AIRCRAFT WOULD NOT PRESSURIZE AND THAT A LOUD AIR LEAK EXISTED AT THE MAIN CABIN DOOR. RETURNED TO DTW WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND THAT THE DOOR WAS NOT FULLY CLOSED. OPERATIONAL AND PRESSURE CHECK OK.