- I did a factory reset, and full update, of both devices.
- I performed various tests from both wireless and hard-wired laptops, to assure myself that there wasn't any NAT / port forwarding funny business going on.
- None of my efforts to date to test the SSDP protocol or the ECP protocol can 'see' my Roku units. (The SSDP tests revealed other devices on my network, so that was interesting.)
- When I look at packet captures, I can see the Roku units originating traffic (pinging my name servers, traffic to/from my gateway, etc.), but I don't see the Roku units replying to packets originated when I use the Roku Android apps, or any of the SSDP or ECP test efforts. They do respond to ICMP traffic, though.
- The Roku app did work for me when I was a friend's house, so I have confidence it's supposed to behave.
If I were to wildly speculate, I have to wonder if that my netblock is different than any of the RFC1918 netblocks is a factor.
I would appreciate any advice anyone could offer toward diagnosing the situation.