Nighthawk C7000 AC1900 modem router ethernet ports not connecting

I just installed a brand new AC1900 Nighthawk C7000 modem router combo in my apartment. This is replacing a previous Xfinity gateway. After installing the new router and activating it with Comcast, I found that while the wifi works perfectly, none of my ethernet connections were working. I reset the router several times and even factory reset it with the hole in the back, but the issue has persisted.

The status lights are behaving particularly oddly. The ethernet status light on the front of the device never turns on, indicating no data transfer. The ethernet port status lights in the back (one green above each port and one amber below) are always lit for ports 2-4 whenever the device has power, even if nothing is plugged into any of those ports. Port 1 is not lit. None of the ports react to the insertion of an ethernet cable to any wired device (no connection is formed and the lights don't change). It is worth noting that when I first set up the router, I connected it to power for the first time with devices connected to ports 2-4. 

The ethernet cables, coax cable, and devices involved (Xbox, smart TV, and desktop PC) are known good, as I previously had them working only a few hours ago with the Xfinity gateway. The wifi is fine as well, as stated; it is only the ethernet module that seems to be struggling. Please give me any suggestions to test further before I have to RMA the device.