ITV updated the app and the software they use is no longer compatible with the box hardware.
TalkTalk no longer provide boxes that record but do supply boxes that are basically streamers and have the update ITVX on them. The 4k box can record via a usb stick, but only has one tuner so you can't record a Channel and watch another.
You might find it best to retain your box to record and invest in a Roku or Amazon fire stick which also include other free to view apps such as Pluto.
If you want a TalkTalk supplied box you will need to phone and recontract with them.
Try phoning 0345 172 0088
Opening Hours can be found here - https://community.talktalk.co.uk/t5/Articles/How-to-contact-TalkTalk-Broadband/ta-p/2230529#
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).
