Please be advised that remotes for Roku TVs are manufactured directly by the TV manufacturer. We would recommend reaching out to the TV manufacturer's customer support team to report the issue and get help.
My remote is doing the same thing. I put new batteries in it and now it is making a high pitched ringing noise but not working. The batteries work in other remotes. Also, I have tried resetting using the instructions on the help pages. I have also tried using the movile app but it cannot find my device.