I'm mainly posting this so that people with the same problem might find this via Google: Symptom: You have registered your Ultimaker S5 for network access via its ethernet port using its MAC address to assign a specific IP address. However it does not pick up the IP address and instead assigns a self assigned 169.x.x.x address. Problem: Some older / enterprise DHCP servers do not like you having an associated DNS if it starts with a number. 3D printers my be more prone to this if like me, you created a DNS "3dprint.myorg.com". Solution: If you do have a DNS associated with your 3D printer, make sure it doesn't start with a number or have a network that sucks less than ours.