When you try to log in to the user quarantine portal or reset the user password for the user quarantine portal, you see the error message.
https://eu.quarantine.symantec.com/
https://us.quarantine.symantec.com/
Error: Login is disabled for user.
Email Security.cloud
Access to the user quarantine portal is disabled from the Symantec Email Security.Cloud portal.
Login to Symantec Email Security.Cloud portal.
Navigate to Dashboard > Platform > User Quarantine Settings
Uncheck > Disable access to Symantec Email Quarantine interface for users (Users will still receive summary notifications)