What you could do in the mean time if you are not planning on changing the unit as yet is change the public ip to the new one.
Ensure that you have a backup of the current setup and go to the settings>parameters. This is usually for advance users but if you understand what it is that you need it should be a cake walk. Most likely you have a static public ip so grab the ip of the old setup and type it into the search bar. Once it comes up you can then edit and save the new ip of the customer. Save and test it to see if it did what you desired.
The fqdn is marked to the unit(mac address etc). However, get customer support to gain back access to the email.