MyBookLive has just simply vanished

If you were set to static on the 192.168.x.x range and you replace the router which has another range, it will fail.

Now, if you are 100% sure the settings have been reset to DHCP, see if you see it listed on the leases for DHCP in the router. 

Not sure how it works on that device, but this might help.

https://discussions.apple.com/message/23991940