Obsidian will not lock if your batteries are too low so as to prevent accidentally locking you out. For information on how to change your batteries, please see the installation guide.
Obsidian may not be locking if the bolt hole on the door frame is not deep enough. Make sure the bolt hole on the door frame is at least 1” deep.
Obsidian may not be locking due to a misalignment with the door, door frame, and/or strike. For more information on how to address misalignment, please see the installation guide.