Mac Mini (Late 2012) cannot connect to the internet via ethernet

Last week we were having issues with our Optimum provided router and we had it replaced with a Sagemcom F@st 5260CV. My Mac Mini was connected to it via Ethernet whereas all other devices are wireless and until yesterday we have had no further issues.

The problems started when I had to move the location of our router to another room. Since doing this, WiFi has continued to work without issue but I have been unable to obtain an internet connection via ethernet on the Mini.

There seems to be a working ethernet connection as I use my Mini headless and connect to it via the app Screens Connect, I am still able to access it when WiFi is disabled. Also, the ethernet cable connector on the Router displays an active green LED.

Things I have troubleshooted:

• Restarting modem & router
• Restarting Mac Mini
• Replacing ethernet cable
• Trying all other ethernet ports
• Clearing browser history and restarting Mac (something Optimum suggested but why I know not)
• Renewing DHCP license (should I be provided with new IP? If so, it doesn't seem to do it)
• System Preferences > Network > Click the lock to authenticate > Location: > Edit Locations... > Click [+] > Name it "New Location" > Click "Done" > Click "Apply
• In Terminal I have tried to ping google.com and my IP address to no avail (ping: cannot resolve google.com unknown host / Request timeout for icmp_seq 0)

My Mac mini (Late 2012) is running macOS 10.13.6. I am in process of doing a MacOS update to see if that has become an issue. Otherwise I am stuck. Optimum have said there is no issue with the router but they have come to this conclusion without troubleshooting it. Crazy Optimum.

Fortunately, I have the WiFi working so it isn't the be all end all. But I use the Mac Mini as a media center and the WiFi can be unreliable so I would really like to sort out this ethernet issue. Any advice will be appreciated, thanking you.