Mike,
I'm sorry for chiming in so late here. I'm an engineer for a certain fruit-themed company, so I have some insight on these sorts of things.
Starting with iOS/iPadOS 14, your iPhone keeps a pretty tight hold on network connections with other devices (like the WIU). Here are a few tips to make sure you've considered that I don't see mentioned in this thread:
1). Go to Settings > Privacy > Local Network and make sure Wi-Fi DCS is turned ON (green).
2). Make sure that you are connected to the correct Wi-Fi network. If you have the WIU connected to your home network (as opposed to having the WIU create its own ad-hoc network), be sure that you are connected to the same network name. Some home network routers broadcast two different networks. One will sometimes be appended with 5G, while the other is not. If your iPhone is connected to a different network, it may have issues locating the WIU.
3). The DCS app running on iOS/iPadOS 14.5 and later can take up to 60 seconds to discover the WIU. After you open the app, leave it on for at least 30 seconds before giving up. You may find that it just takes a bit of waiting before you can successfully send a READ command to the WIU for the first time. Once it's connected, there shouldn't be any more waiting.
This isn't to say or imply that the DCS app doesn't need work. It does. Lionel's apps are also one critical OS update away from inoperability, it seems. There's so much untapped potential in mobile computing for these platforms--let's hope it's addressed sooner rather than later.
Rafi
