error 401 accessing mailbox of admin for MNE during first configuration

Hi all.

I am trying to configure Migrator for Notes to Exchange for the first time to migrate Domino to Exchange on premise.

I created a user in my exchange 2019 to act as an admin for the migraiton.

i give him the receive-as permissions on the database.

outlook 2013 pro plus and latests patchs applied, it is connecting well to his mailbox.

but when i configure the Exchange part on MNE, i got an error:

unable to open target mail store

and in console logs:

Microsoft.Identity.Client.MsalClientException: User realm discovery failed


System.Net.WebException: The remote server returned an error: (401) Unauthorized.

login for y admin user and password are correct as they works in outlook and even in owa.

So where can i check for more error report or do i need to change something in configuration ?