Username displays as "Player"

Conditions:

Successfully signed-in to Microsoft account / good internet connection / updated (most-recent) game version / updated Windows platform / etc //

Issue:

While signed-in to Microsoft account, the word "Player" displays as username on both the main menu and non-local multiplayer. (this was tested using another account from a Nintendo switch)

Notes:

This occurred immediately after being removed from a Realm player whitelist //