I have a hosted BDS server and I have players whitelist/allowlisted within the alllowlist.json file, but the issue I'm seeing is if the don't have their XUID within the file they are unable to connect to the server.  Usually, to my knowledge, the allowlist.json auto-populates the XUID information after the first connection made by the player without that in the file.  This isn't happening because it tells them they are not invited and blocks that connection.

Microsoft/Xbox gamertags are correct and cased correctly, so that's not the issue.  It was doing it to me in testing with correct casing.