It seems like the issue might be related to the modem provided by your Internet Service Provider (ISP). I recommend checking the WAN IP address in the modem’s web interface (GUI) to help isolate the problem. This will give you a clearer idea of whether the issue is with the connection or configuration. If the WAN IP address is missing or incorrect, it could indicate a provisioning issue that might require support from your ISP.

also check your power supply. I’ve seen a user use the wrong power supply (from their switch). It supplied enough power to get their device booted but anytime it tried to use wifi or other services, it’d crash as the router tried to pull more power. 

Thanks for your replies. I verified the power supply is correct, and don't suspect this is an issue because things were working for a few days just fine.

I've now narrowed it down to the wifi signals being active at all, whether any device is connected or not. If no wifi signals are active, the ethernet works fine. I reached out to my ISP (Xfinity) and they say everything looks fine on their end, but I don't know what level of support I've dealt with to know that's accurate.

Got a screensnip of the cable connections page? 

When you’re testing the wifi, try powering off your wifi devices and slowly turn them on and test them. I’ve had also had a sketchy wifi device that caused issues before. 

I don't have a screenshot right now, no. I went into all devices and deleted the wifi, I also factory reset the router so it's used the default wifi names and no device recognizes them. I want to believe it's an ISP issue, but I'm not sure how considering ethernet works with no issue.

Since Wi-Fi name is not broadcasting on any of the devices, could you let me whether the Wi-Fi LED light on the modem is ON.

If the LED is solid on the modem for WIFI, please login to web portal and change the Wi-Fi credentials and check whether Wi-Fi name is broadcasting on your devices.

If there are no changes on the behavior, please factory reset the modem without co-axial cable for 30seconds.

Sorry, there's a miscommunication here. The devices can see the signal fine, but I am not attempting to connect them to the signal. The issue is that if any wifi signal is being broadcast, it shuts down.

Could you try connecting the modem with different power outlet?

Not sure about arris products. but my CAX80/CAX30 from netgear will auto-reboot if they don’t detect a signal from the ISP. Its not a good design. Not sure if Arris uses the setup. Once the router is up and running, check its cable connections page to see the quality of the connection