This article explains how to re-pair a Roku Enhanced Remote.
How to Reset Your Roku Remote
Whether you’re using a Roku box or a streaming stick, if your Enhanced Remote decides not to cooperate, it’s most likely lost its pairing. Enhanced remotes either have a single pairing button or a pairing button with an indicator light.
Here are the steps to re-pair your Roku Enhanced Remote.
Remove the battery cover on the bottom of the remote control and remove the batteries.