All lights are on the modem and it looks just like normal when it stops working. When looking at the router page, it is not getting an IP address from the modem. The ASUS router gave the error "your ISPs DHCP service isn't functioning properly" or something to that effect, the edgerouter just shows as no data.
Plugging in directly doesn't work either. Resetting the modem from the Cox webpage seems to work better than just cycling power, and that seems like the only way to fix the issue when it goes out. Went out around 11pm last night, got it working this morning with a reset, and it stopped working again a few hours later.
If it's consistently an issue with DHCP, you may need to describe your network topology. What's directly connected to the modem? What's connected to whatever is directly connected to the modem? What device assigns IP addresses to your clients. Are your clients configure for static address?
Cable directly into modem, modem directly into EdgeRouter X (or Asus AX3000), EdgeRouter has a few access points and hard wired connections going into it. This is also a new issue in the past month or two. I think another poster may be on the right track with IPv6.