Not sure what you mean by 'i have disconected my sky service'. I assume that you mean you canceled your subscription but carried on watching FTA and FTV channels? BTW you need your old Sky Vieing Card in the box to watch some FTV channels. If you took the Viewing Card out of the box it will have failed to get it's 'Stay Alive' signal and that can take up to three days to recover.
If you are getting no signal then something other than the fact that you were only watching FTA and FTV channels has happened. e.g. Dish misalignment, bad LNB, bad coax or connectors.
Here is what you can do. Remove the Viewing Card, unplug the box at the mains, check the coax 'F' connector is tight. Leave the box for a few minutes and then plug it back in. At some point you will be asked for the Viewing Card, insert it. Remember though if you took the Viewing Card out of the box it take up to three days to recover.