Since yesterday (10/12/22) The channel selector does not "frame" the channel/app as you scroll through the channels/apps- you have to "read" which is the currently selected channel/app at the top of the screen. This is bad in so many ways. Please fix this.
Try changing the Theme and Wallpaper in your Settings to see if the "frame" (highlight box) reappears.
Navigate to Settings/Theme for both the theme and wallpaper selections.
Otherwise, post back with Roku model number and Roku OS (both found in Settings/System/About) and where you are seeing this behavior. (Home Screen, Search screen, all screens etc). Also post back with the current theme and wallpaper you are using and will see if can duplicate.
Can always Factory Reset (Settings/System/Advanced System Settings/Factory Reset) as a last resort. Make sure you have a physical working remote before factory resetting any Roku device.