If the email says it sends without any errors it typically means it's failing at the mail server. Within CB > Configuration > Registration ensure the From Address is valid for your domain or left empty so it uses whatever is set in Joomla global configuration. Try contacting your host and have them check the mail server logs to see if there's any outbound emails being blocked. It's also possible the emails are sending, but are being put in the spam folder so be sure to check your emails spam folder.