The app can only identify Roku devices that are on the same network as the device with the app, the network must use a private IP address range, and the network must not have any security setting enabled that blocks connected devices from seeing other devices on the network. If those three requirements are not met, the app will not be able to connect and control a Roku.
If you are using a public WiFi (shared in an apartment complex, hotel, dorm, etc.) the security setting I mentioned is absolutely enabled and they won't take it off for you.
Dan
Roku Community Streaming Expert
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