Hi @Mohammad_Kamal,
Thanks for reaching out about this here in the Roku Community!
This issue could likely affect the TV hardware's backlit. If the issue persists even after unplugging it from the power outlet, then this is an indicator of the issue. For further assistance, you may need to contact your TV manufacturer directly. Each Roku TV manufacturer provides direct support and warranty services for their products running the Roku OS.
For a list of Roku TV manufacturer's contact information, visit our Community post here: Contacting Support for Your Roku TV.
We hope they will be able to extend it for you and get back here if there's anything else we can further assist.
Regards,
Rey
ERey.
Roku Community Moderator