The IP address is assigned by your router and your TV doesn't have one until it's connected to your network. If you're trying to use the app on your phone as a remote you won't be able to do that until your TV is connect to your network/Wi-Fi. If you can use an Ethernet cable to connect the TV to your router then it should connect and get an IP address, but you'll have to go into your router's settings to find out what it is if the app can't find the TV. Otherwise, if you're trying to get this TV connected to your Wi-Fi then you'll need a physical remote. Note that Roku Simple remotes don't work with TVs, so you'll need either a Roku Voice Remote, a remote from your TV's manufacturer (which isn't Roku), or a universal remote that supports Roku TVs (and not just Roku streaming players).
If I've misunderstood what's going on give us some more information about what you're trying to do and why you think you need the IP address.
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