Roku factory reset and no remote

The reason it can’t find the device is because it isn’t connected to a Network yet. The only way to Use the remote app, instead of the physical remote, is if the streaming device/TV has already been connected to the same wireless network as the device with the remote app. Obviously, if you’ve already done a factory reset, It won’t be connected to any network anymore, So the only way to connect it to a network is by hardwiring it or getting a replacement remote