Ethernet Port missing, iMac 12,2 Yosemite

Greeting

I recently bought a pre-owned iMac 27inch. Works fine, connects to wifi etc. Few days back I needed to connect some devices through its wired ethernet port. Plugging in the LAN cable iMac didn't connect to the network switch, connectivity LED on the Switch didn't light up. I have done fair bit of troubleshooting but nothing seems to help resolve the problem.

About This Mac–System Report–Hardware–Ethernet Cards says "This computer does not appear to have any PCI Ethernet cards installed".

System Preferences–Network list of Interfaces on the left side had an entry for Ethernet but Advanced-Hardware tab for this did not show any MAC address.

One suggestion on the internet was to delete this Interface from Network Preferences and re-add the same. After deleting this from the list of ports I am unable to add back as this port is not shown in the list of Interfaces that can be added.

I have also run the ASD on this iMac but there are no specific tests for ethernet port.

Using ifconfig on the Terminal App does not list en0.

Some related sreenshots are included for additional information.

Would be grateful for any help and thank you for reading through this.