try activating the lock mechanism to the locked position when the door is open, before inserting the cylinder. Often this is simply an alignment issue. Many installers forget to read the instructions (i am not saying you havent).
One One was a race horse, one one won one race, one two was a racehorse, one two won one too.
Disclaimer: Do not pull tag off mattress. Not responsible for legal advice while laughing.
Bilock - The Original True Bump Proof Pin Tumbler System!