Could not Get Data SharePoint Onlie list through Organizational Account

Hi,

When I tried to Get data through SharePoint Online List with URL like 'https://portal.company.com/sites/project/Public' using Organizational Account. I'm getting the following error when I click on 'Sign In' button under Organizational Account.It didn't even ask for the credentials.

The WWW-Authenticate header doesn't contain a valid authorization URI. Header value: 'Basic Realm="portal.nttdata.com"'.

Could any one please help?

Thanks.