In Powershell, I executed the below cmdlets
Connect-MsolService
Getting error like below
Connect-MsolService : Your credentials could not b
I had excatly the same problem. I solved it with creating a new Global Administrator as already mentioned.
Just wantend to state that:
-this must be done in the old portal, not the new one
-adding a native account to that AAD B2C, guest accounts do not work
The account you are using must be assigned the role of (Global) Administrator in Azure Active Directory as stated by the document you referenced:
Before you can create applications or users, or interact with Azure AD at all, you will need an Azure AD B2C tenant and a global administrator account in the tenant.
By default, all co-administrator accounts are added to Azure AD in 'Member' role.