Can't start with jumper leads, immobilizer light on

Hi my aged parents have a 2010 Getz, the inside light was left on while parked in the garage and ran the battery flat. The remote would not open the car and I needed to open it with the key. I then connected jumper leads to another car but the Getz will not start the imobilizer light comes on (yellow light with a key shape inside). Can someone help me with a solution?
thanks! John