Generate username after registraion

I found this topic:

https://www.ads-software.com/support/topic/auto-generated-username-ultimatemember/

But it didn’t work for me. I use the same code, only in my case the meta key is called verein_name. However, the user name is always saved as the standard combination: firstnamelastname
Has the procedure changed here?

This is my code in the functions.php:

add_action("um_registration_complete","um_042121_change_user_role", 1, 2 );
    function um_042121_change_user_role( $user_id, $args ){
        try {
            if( isset( $args['verein_name'] ) ){        
                wp_update_user( array( 'ID' => $user_id, 'user_login' => $args['verein_name'] ) );
            } else {
                wp_update_user( array( 'ID' => $user_id, 'user_login' => $args['last_name'].'-'.$args['first_name'] ) );
            }
        }
        catch(Exception $e) {
            echo 'Message: ' .$e->getMessage();
        }
    }

Am I missing something?
Thanks in advance

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