As an Administrator you are still unable to view all emails in the Quarantine portal even though you have the correct permissions.
Email Security.cloud
The main reason is due to the Global settings vs the Custom settings that has been assigned to your organization's domains in the client net portal.
Ensure, that the created Administrator account is on the same Global settings and not on Custom by checking this path : Dashboard > Platform > User Quarantine Settings
Assuming, that your domain using Global settings under User Quarantine settings as shown below :
Your Administrator account must exist under this settings Tab. If the domain is using Custom settings as shown below :
Then you may need to add your account under the custom settings if you do not plan to change the domain's settings to Global , or simply select Global Save and Exit.