As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED DEPARTURE DUE TO A VENT SKIN VALVE FAULT AFTER TAKEOFF. THE OUTFLOW VALVE WAS INOPERATIVE & UNABLE TO PRESSURIZE CABIN. NO EMERGENCY DECLARED. LANDED WITHOUT INCIDENT. MAINTENANCE PERFORMED TSM 21-26-00-810-804-A AND AMM 21-26-00-710-001-A. ALL TESTS SATISFACTORY, NO FAULTS GENERATED.