No Talktalk are not responsible. Access is fine.
You sometimes have to wait quite a while for the red button access to appear. I am assuming you can access other Internet channels (free sky ones) and the on demand players.
If you feel the access is not working try resetting your box. Turning it of and then on at the back does sometimes help before doing a full reset. if that does not help then try a YouView Reset and choose option 4 (Internet/USB Recovery, keep recordings) to keep recordings. I would also suggest that you try rebooting 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 leave it for an OCE to do further checks.