I'm able to access the Rain Machine on both my computer and iPhone through the web browser using https://local-ip:8080 but the same iPhone using the app can't find it locally and can't connect when I set up Direct Access in the Network settings. I've set the Local Network to On in the iPhone Preferences. I've also set up port forwarding on my Eero on that local-ip to 8080. 

It doesn't seem to be a network or 2.5 Ghz vs 5 Ghz because I'm able to connect on my iPhone through the web browser.

This just happened, as the app was working earlier in the week. Then, logging into the website I had to create a trial remote access account before I could do anything.