It seems to be a bug when upgrading I think.
I had to reset the lock screen data to get them back for mine which you can do by going to Settings->Lock Screen and AOD->About Lock Screen->Tap the info icon in the top right corner (should take you to the AlwaysOnDisplay app info page) then go to storage and tap clear data. Just bare in mind this will reset the lock screen and always on display layout (doesn't affect your passcode, fingerprints etc just the layout like the clock position and style and such)
