Office 365 synchronization fails:
Failed to add 3 user(s): - firstname.lastname@example.org (Missing or invalid default region.) ...
Software-related issue #APSA-15355: "Synchronization ignores the user countries that aren't in hard-coded list of countries".
Office 365 accepts the only hard-coded country codes from
In this case, user1 had
España instead of
Spain in its contacts.
Contact TAM or PTA to trace the status of the request.