XF 2.2 Alerts not being received - flow chart?

[Mouth]

Is there a flow chart for diagnosing a user saying they are not receiving Alerts for watched threads?
How do you determine the cause?
Account Preferences - Alerts not set correctly? But how does an admin see a users settings?
Not read/visited since previous Alert? But how does an admin determine this?
... etc.

 

[Orit]

There are addons to login as user and view their settings.