It may happen that you do not receive a reply from guides. In that case, your guides may just be extremely occupied or without the internet connection.
In such cases, give them some time and wait; In many instances, your guide simply missed the notification for a message, so send them a message to notify them. In an event where you still do not get one, giving up is probably your best option. There are many guides who can show you around, so please find other guides again.