What happens if you press the record button on a channel you are watching? does this fail?
Sometimes turning the box off at the back and then on again can cure this issue. Try this first and then try recording while watching and set up a program to test.
If it still fails then try a YouView Reset and choose option 4 (or Internet/USB Recovery, keep recordings) to keep recordings. I would also suggest that you reboot the router once you have reset the box.
If this works, you will need to reset your future recordings and personal settings. When you select a Sky channel you should then be asked if you wish to set up the channel again.
Let us know how you get on, and if it does not work then I'll flag it for an OCE to do further checks.
Alternatively if you still have your BT box you could use that as your primary box if it is a YouView box and still works. The OCE could switch it for you.
As said please let us know how you get on either way.