Have you tried turning the box off at the back and then on again? This sometimes cures this as does a YouView Reset. 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.
Please let us know how you get on either way.