Yes, if it by chance had been factory reset, it would be back to .0.1 address. Which you might want to do anyways, reset and set it up again. Doesn't take long. Try using .0.50 as the 615s address. Ensure that no other devices are using the same IP address as the 615. Turn off ALL features on it, SPI, uPnP, DHCP and all Filters as they can not be used in this configuration. Don't set up a reserved IP address on the main host router for it. It's not needed as it has a static IP address on the 615 in this mode.