Ethernet has self assigned IP and will not connect to internet.

This typically indicates that your Mac cannot contact a DHCP server to get its proper IP addresses to be able to connect to the network. In this case over an Ethernet connection.

What have you tried, so far yourself, to resolve this other than just posting here so that we don't try offering you potential solutions that did not already work for you?

Do you know what the router IP address is? If so we may be able to advise a fixed IP configuration to get you online.

Excellent! I'm glad you got it worked out.