And tuning to Ch.410, Ch.411, Ch.417 and Ch.421 gets you a no signal warning?
If you try Ch.868, what do you get?
Also, do you have TNT Sports HD or TNT Sports SD?
Are you able to view BBC One HD on Ch.101?
Yes
Same message or sometimes scrambled screen
Don't know
Yes
One final question:
Do you have any other signal issues on any other channel?
No, all's fine.
Your only option then is to contact Sky and report a fault with your dish/box and arrange a visit from an installer to check your kit. Its possible your dish needs rechecking.
Im sorry i can't be of more help.
Thanks for trying - greatly appreciated.