One or more users are unable to access the email quarantine to retrieve quarantine messages.
This could be either due to:
Email quarantine users should use the new Symantec Email Quarantine URL based on the company's geographical location, unless it has been requested otherwise upon provisioning.
Quarantine administrator can force an individual or all user to change their password, this would generate an email to the user with the correct Quarantine PEN URL.
To force Email Quarantine password reset
A quarantine administrator can also make sure that the user is accessing the correct URL, below are the current email quarantine pens based on the different regions: