Have you checked the batteries?
Have you tried resetting and pairing the remote with the box?
Details can be found here
https://community.talktalk.co.uk/t5/Articles/TalkTalk-Remote-Control-Guide/ta-p/2204370
Please remember to mark Solved Posts with Best Answer. Doing so helps other customers and saves TalkTalk's Support Team time by only looking at unsolved topics. Thanks, Steve (a fellow customer).
