Upgrading the firmware reset both the devices to have static IPs, this is why they were not showing up as connected on my network. Once I connected to them directly and went to the WebUI using the default IP of 192.168.254.254, I was able to get them reconfigured and working again.

As I stated in the OP, I've already done this, on both devices. I'll try again.

As I mentioned in the post, the devices are no longer showing up as connected devices on my network after the firmware upgrade. I can't get their IP addresses, so I can't get to the WebUI in order to check or change any settings.