As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT AT APPROXIMATELY 2000 FEET MSL THERE WAS A LOUD THUMP AND OUR EARS POPPED. DURING CLIMBOUT THE PLANE WOULD NOT PRESSURIZE. RETURNED TO FIELD. LANDING UNEVENTFUL. REMOVED FROM SERVICE. PLACED PRESSURIZATION SYSTEM ON MEL 21-30-5A. RETURNED TO SERVICE.