As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT, DIVERTED. ACFT FAILED TO PRESSURIZE AFTER TAKEOFF. AFTER DEBREIFING CREW WAS REPORTED MCD SEAL FAILED TO INFLATE. WARMED/HEATED/ CLEANED SEAL AND AREA, GRD RAN AND PRESURIZED IAW AMM REF 21-00-00-863-801. PRESURIZATION AND MCD SEAL OPS CKS GOOD. RETURNED TO SERVICE. NO PARTS REPLACED.