As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT, GOT A "CABIN ALT" CAUTION MESSAGE WHICH OCCURED AT FL230. CABIN PRESSURE WAS RISING RAPIDLY. DONNED MASKS AND "CABIN ALT" WARNING MESSAGE APPEARED. EXECUTED EMERGENCY DESCENT, RAN QRH. RETURNED TO FIELD. INSULATION BLANKET WAS FOUND STUCK IN THE SECONDARY OUTFLOW VALVE. REMOVED BLANKET AND OPS CHECKED IAW AMM. OPS CHECKED GOOD.