Nighthawk X6S - Can I use Ethernet instead of WiFi as internet source?

I have a Netgear Nighthawk X6S wireless mesh extender. Since it has been installed I have now had on opportunity to run an ethernet cable to its location. I hoped that I could plug the ethernet cable from my router to the X6S extender so that it would have a wired connection back the the router and then let it behave like a Wireless Access Point.

However as soon as a plug the ethernet cable in all the devices on the extender lose connectivity.

I am guessing I need to replace it with an actual Netgear access point. However the X6S was quite expensive and I wondered if there is any way at all to try and get it working like an access point to salvage the purchase? I am probably clutching at straws here but just thought I would ask and see!