It’s one of 2 things (assuming the ST mobile app and SmartApp notifications are enabled):
- The lock isn’t sending the code used information, this typically shows up as unlocked notification with no user name in the activity tab
- The most common lock mesh list event issue (you don’t see a notification in the lock activity tab or don’t see the user name), see this topic on how resolve it: FAQ: why would I need another beaming repeater if my zwave lock is already close to my hub?
Also see the LUM FAQ doc.