As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMBOUT AFTER SWITCHING BLEEDS FOR SINGLE PACK OPS, HEARD A CLUNK, AND THEN NO AIR COMING OUT OF VENTS. CABIN ALTITUDE CLIMBED TO 690 T-INDICATING PRESSURICATION STOPPED WORKING. F/A REPORTED MILD BURNING RUBBER ODOR IN BACK OF CABIN. FOUND PRIMARY INLET DUCT TO HEAT EXCHANGER LOOSE, RESECURED, OPS CHECK GOOD IAW AMM 21-51-07.