How to troubleshoot door lock issues when a hotel key card won't open the door?

When a hotel key card won't open a door, guests usually just assume the front desk didn't program the card correctly, but there can be many reasons on-site. Key card degaussing, low battery, unsynchronized door lock time, failure to update room status, or failure to deactivate an old card after a guest changes rooms can all result in the door not opening. If you're on the night shift and handle…