If you have added a manager to your account and they also work as an employee, they will have two usernames and passwords.
Occasionally other employees will message a manager at their employee account instead of their manager account. The manager may receive a forwarded email but not see that message when they sign in as manager.
They can login using their employee username and see that message in their employee MESSAGING section, and they can remind employees to message them as a manager instead.
Some managers like to edit their own employee name to just initials so it is less likely employees will message them there.