I have checked that my devices and mobile app are on the same network, restarted phone and Roku devices, uninstalled and reinstalled the app as well as tried connecting manually. None of my 4 devices will show in the Roku app.
It's great to have you with us here in the Roku Community, @DMT321!
We understand how inconvenient this issue can be for you. We want to be able to help you look closer into this so we can get this sorted out.
Here are a few things we can check:
We hope this helps. Let us know if this works for you.
Best,
Emman
Some routers have a setting that prevents multiple devices on the network from "seeing" each other. This is mainly used on shared networks like in a hotel where you don't want to open up your devices to everybody else using the same network, but it might be enabled on a private home network.
What make and model router are you using?