https://stackoverflow.com/questions/39657391/login-azurermaccount-cant-login-to-azure-using-pscredential/39675182#39675182
Atf's answer has a point but however, this is not only the issue. We cannot directly sign in non-interactively using Hotmail or Outlook account. You must use domain of your account to sign in.
See a similar issue posted in server fault : https://serverfault.com/questions/746557/add-azureaccount-unknown-user-type-unknown-user-type-on-azure-automation/746673
It mentions:
Make sure the credential asset name (not username) is a simple string. Also make sure the credential asset username is a valid OrgID user (ex: abc@fdgdf.onmicrosoft.com), not a Microsoft / Live account (joe@gmail.com).
