As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED THAT AFTER TAKEOFF AND DURING CLIMB OUT PASSING 5000 FT, NOTICED THE ACFT WOULD NOT PRESSURIZE. SELECTED MANUAL MODE AND ACFT STILL WOULD NOT PRESSURIZE. DISCONTINUED CLIMB AND DIVERTED. AFTER TROUBLESHOOTING ACFT PRESSURIZATION SYSTEM, FOUND THAT THE PRESSURIZATION MODULE CONTROL SYSTEM VACUUM RELAY HAD FAILED. R & R THE VACUUM RELAY, MX PERFORMED AN OPS CHECK WITH NO DEFECTS NOTED. ACFT WAS RETURN TO SERVICE.