If you are getting the message "no signal" this would indicate that there is a problem with the signal from your dish into your box. Even without a card inserted into a Sky Digibox, if there is a signal, you will always get Sky Guide and the free channels.
Try powering off your box, remove the card, check carefully the cables, especially the connection to the dish, reapply the power and then when asked to insert your card you should then be able to see (for example) Sky News on 501 and the BBC News channel on 503.
Once you can see any channel, reinsert your card. This should, after about one minute, give you the channels you expect, such as 103, 104 and 105.
If you continue to get "No signal", you dish may have been misaligned, or there may be a fault with the cables and connectors, or a problem with the Digibox. You can see the signal strength by pressing SERVICES, then 4-SYSTEM SETUP and 6-SIGNAL STRENGTH.
May I suggest that you perform a complete shutdown of your Sky box, by turning it off with the remote control (so even the faint green light goers out) and then unplug the mains lead either from the wall socket or from the back of the Sky box. Wait at least 2 minutes, then put the mains plug back in again and wait a further 5 minutes. That is tio allow the box to reset it's memory of available channels. After that turn everything back on and check what channels you are getting, programme 101 should be your local BBC1 service.
I have lost all of the BBC chanel's on both my free view box and free sat box ( upstairs and downstairs ) not sure what to do I am an older person so cannot get up in my loft to sort out the aerial or the booster cables and can certainly not able to get up to o the sat dish , but surely if both are failing it cannot be a fault in freesat or digital.......HELP !!!!