It may be worth you copying it and saving on your computer as I have had to use it several times over the years. It cures all sorts of things, channel tuning problems, internet connection problems, remote not responding and many other things which you come across as it reinstalls the main software, so any minor data corruptions in the operating system are often fixed.The basic instructions are on the Youview site under Maintenance Mode Reset. I added the other bits following my personal experiences.
If this doesn't work then the "factory reset" from the main YV menu can often get the box working again but, it wipes your recordings as it also fully re-formats the hard drive.
If this has helped and solved your problem, please mark it as Best Answer so that OCE's or others do not spend time looking for alternatives.