Perhaps you might want to write an additional:

If you think you're doing everything right and still cannot access the shell-mode (or give any other commands through the serial connection), please check that your terminal settings' RTS/CTS flow protection has been turned OFF (default is usually ON).

Just after the "If your player is working properly, you can control it at this point by typing commands such as N (Enter) for the next track. A full list of commands can be found at the developer's site."

Your call, of course, though!