Hi,
What do you mean by "portal"? Office 365 account?
If you mean the web mail, as here we mainly focus on issues regarding Outlook desktop client, I'm not familiar with web mail. You could first click "Can't access your account?" to troubleshoot this issue.

If this is not the case for you, I'd like to know if there are any error messages. If yes, please paste here for further assistance.
Please also provide more details about this issue so that we can do more research.
Any updates, you can feel free to tell me.
Regards,
Perry
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