Your remote is IR (infrared) so there is no pairing. It sounds like a contact on the remote has failed. You can test it by using a digital camera, such as what a smart phone has, and look at the front of the remote when the buttons are pressed. If you see a flashing light through the camera when pressing a remote button, the remote is working. Try several buttons on the remote, including the mute button. No flashing light, the remote is defective. Since it's only 3 months old, it should be under warranty. However, you would have to contact the TV manufacturer for that support, not Roku.
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