I know I know. Thread Necro. But my comments are very pertinent to this particular situation.
I experienced the same exact issue this morning. I also have a similar setup including Comcast, Arris 6141, pfsense box (not exactly the same hardware.)
I have had this issue for years now and no matter what pfSense version I’m using, it appears to occur on my box after power loss to both pieces of hardware. Now I unfortunately don’t know what is actually causing the issue, however, these are the steps I took to get back up and running:
Powerdown and disconnect pfSense box from power.
Disconnect Arris Modem from power and ****disconnect the Ethernet cord from the back of the unit. (****Disconnecting the ethernet cable seems to be the key here.)
Reconnect pfSense to power and boot all the way to the options console. (No WAN IP listed at this point)
Connect power cable to modem and allow to boot all the way until you have Green, Blue, Blue, Green Solid LEDS from Top to bottom.
Finally, plug in the ethernet that attaches to your router into the back of the modem and wait for a few seconds to see the last LED (pulse wave logo) on the modem illuminate and start blinking blue.
Refresh the pfSense console by just pressing enter with no options input.
Did you get a WAN IP?
Give this a try.
Edit: I just read that you have already decommissioned the machine to other duties. Maybe this’ll help someone else if they stumble upon your post in the future. Cheers.