Not Receiving the Emails for subscriber in RTC 5.0.1
One answer
The only explanation I have would be to check the user profile editor --> "Mail Configuration" tab --> subscriber check boxes (perhaps some are unchecked). It sounds like you may have already did this though.
In your question, you are not really describing who made the change, and what type of change (which might be useful information to have, just to rule out that something uncommon is being performed).