new ignition barrel and key fitted won't start car?

My 1999 citroen saxo east coast wouldn't stop when I called in fuel station. The ignition had to be dismantled and battery disconected to stop engine running. Have new ignition barrel fitted, but tried to start with the new key, I didn't realise the key was chipped, all the warning lights flashed and the engine wouldn't even try to start. We then took the black cap and chip off the old key and changed it on to the new key. The electronic ignition key symbol on the dash doesn't come on now but the car still won't try to start. Anyone able to recommend what else we can do. PLEASE.