@Welderand @PrincessR , you'll see many, many posts here with the same problem. The TV's backlight has probably failed. You can try a factory reset, but I'd be surprised if that works. If it's still under warranty, contact the manufacturer. If not and you're very handy, you may be able to find instructions on the web for what needs to be replaced. If the manufacturer was other than Roku, don't expect any help from Roku. Sorry for the bad news.
How do I factory reset my Roku® streaming device? | Official Roku Support
Where can I get support for my Roku TV™? | Official Roku Support
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