We are gradually converting the Azure AD authentication provider to a new Microsoft authentication provider. This option only works after you have received a message from your Blue10 administrator that your environment has been migrated to use the new authentication provider. If you haven't heard from your administrator yet, click 'Cancel' and then use the Azure AD or Microsoft button you used earlier.
Have you received a message from your administrator that you have switched to the new authentication provider? then click 'Login'. You will then be redirected to the Microsoft login page.