Try unpairing it and see if in IR mode it is responsive.
If it is responsive in IR mode (obviously you need to point the remote in the general direction of the box), then maybe there is an issue with interference with the bluetooth. Is the box located next to any other wireless devices (Router, cordless phone, etc..), or even some motor load (like a portable AC or something) ? If TV has wifi on it, try just as a test, to disable the WiFi on the TV.
For the remote, when I mentioned earlier about dropping it, it is not always a drop. Sometimes it can happen if for some reason someone sits on it, or rolls over on it (plenty of mine split open on occasion if I forget them on the couch and site on them). It is very subtle if you are not looking at it from the side, so you may not notice it, but it raises the plastic ever so slightly that the buttons are no longer "raised". Anyhow, you can see the pics attached, First one is slightly split along the edge and you can see the buttons are flush because of that. The second pic, with it squeezed back together the buttons are raised, making them easier to use and more responsive. Anyhow, just something to check, since I have had 2 friends who have had that issue, and we got a good laugh when I went over and just squeezed the remote back together.