Hi Carol
If you press the services buton on your sky remote then select option 4 then option 6 this will display the signal strength and quality, if it does not show any then either the signal from the sat dish is not getting through to the box, check the wire that screws into the back of the pace box, or the box itself has developed a fault
hope this helps, if you are local to somerset I would be happy to have a look
nick