If it worked, then stopped working after it was imported, then the file is corrupt, and likely that Scan to destination was the reason you were getting the false error Display name already exists.
Just delete that address book entry and start again.
If it is a new entry that is failing it is likely just formatting of the username. The Connectkey products are very specific, and in 95% of cases you can't use a hostname (Has to be set to DHCP and registered on a Domain)
So check the properties of the folder and match your login to the part in brackets as highlighted here. it doesn't matter in the least that other printers are using a different format, this one needs it how Windows shows it.
