These box are now approaching end of life and are no longer supplied by TalkTalk. They now only provide a box that streams.
have you tried a YouView Maintenance Reset (https://community.talktalk.co.uk/t5/Articles/How-to-find-maintenance-mode/ta-p/1429347)?
Try the Factory Reset keep recording option.
You will then need to reset your personal settings (such as parental controls / Set antenna Out to On in Settings: Picture and Sound / Surround Sound etc.) and also reset your scheduled recordings (might be worth taking a note of future recordings before doing this so you don’t miss any).
If all else fails then try a full factory reset from the settings menu. You will lose your recordings but if being able to record is important to you going forward, it the final option to try.
Hope it works and let us know how you get on please.
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).
