We installed the most compatible AEM Screens Player version to the server's version (that is 6.4.2), Then configured the player to connect to the server. But the player fails to generate token, with the status under System Information "initial (link-up) (unauthenticated)".
System wide user password restrictions might cause failure in the device registration. The device registration uses a random generated password to create the device user.
If the password is restricted by the AuthorizableActionProvider configuration, creating the device user might fail. I request you to try removing any password restriction at