The obsolete SMB v1 supports anonymous logins without authentication (the very reason why it is considered insecure, it’s usage is discouraged and it got declared as obsolete and deactivated by default on Microsoft Windows and most (all?) other modern OS distributions) while SMB v2, which is also supported by ROCK btw., requires authentication (like Guest, Guest for example).
Note: try Anonymous as username to login, it helped at least one other user.