What was found
AFTER DEICING & A NORMAL TAKEOFF, ACFT DID NOT PRESSURIZE. MFD INDICATED CABIN WAS CLIMBING WITH ACFT. FOLLOWED BY AN AMBER CAS CHK DOORS & CABIN DOOR OPEN. ICE PROTECTION WORKED NORMAL ON TAKEOFF & APPROACH TO LANDING. DURING APPROACH CABIN PRESS CONTINUE TO DESCEND. R &R THE DOOR THRESHOLD HARNESS. OPS CHECK OF DOOR SEVERAL TIMES & COULD NOT DUPLICATE SQUAWK. CHKD RIGGING OF VENT DOOR PROX SWITCH & FOUND OUT OF LIMITS. RIGGED VENT DOOR PROX SWITCH & OPS CHKD, NO DEFECTS NOTED. VERIFIED RIGGING OF PRESSURE PREVENTION PANEL WITHIN LIMITS. POWERED ACFT & PRESSURIZED WITH APU, NO DEFECTS NOTED. DOOR OPS CHKS COMPLETE, NO DEFECTS. WORKED IAW AMM 52-10-04. 52-70-10, 21-30-00, & 52-70-00.