I sometimes find that the box needs resetting especially after some software updates. I see you have turned off at teh back and this improves it sometimes.
Therefore I suugest that you try 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 also make sure you have your personal details in your profile complete to facilitate their help.
Please let us know how you get on either way.
Good luck.