@Tracy1222,
There are certain things regarding the management of my rentals that I won't leave in the hands of automation with a third-party. I've always manually generated the door codes using the last four digits of the guest's phone number so it's easy for them to remember, and send it to the guest. This allows me to set the active duration for the code. As you've experienced, the Airbnb CS reps don't have knowledge about doorlock integration, and would be of no assistance to your guest or you if there is an issue with the door code.
Issues with access to the rental will frustrate or anger the guest, and can lead to Airbnb imposing punitive action against the host. IMO, it's best to control as much of the rental process as possible.