I have installed Azure AD Powershell.
To use it, I get credentials with e.g. $AzureAdCred = Get-Credential
I am prompted for userid and password. The 365 Identity / Enterprise applications sign-in log says these were accepted successfully. All apparently good so far.
I then try to connect using Connect-AzureAD -Credential $AzureAdCred and receive the AADSTS50076 error.
The 365 Identity / Enterprise Applications sign-in log says:
Status : Interrupted
Application: Azure Active Directory PowerShell
Additional Details: User needs to perform multi-factor authentication
However, the MSFT account has long had MFA switched on, but neither the Get-Credential nor the Connect-AzureAD gave an MFA prompt.