In order for MusicBOT to send you a message - in this case a list of available commands - the necessary permissions are required:
b_client_channel_textmessage_send ⇒ Allows you to send text messages to the current channel.i_client_private_textmessage_power ⇒ Specifies user or group permissions for private text messages.If the above permissions have been set appropriately and have no effect, check that you do not have a spam-blocking plugin.