If you have knowledge in repairing then try the following but frist try solution from Henry
First locate your steam pump most coffee machine I repaired have steam pump seperately, so you need to run the pump directly to the power it should be rated on how much voltage it works with. if the pump does not work then you need to replace it remember pump can be repaired also.
If the pump works then you have problem some where else that is the driver for pump mostly electronic board.
Try upto here n tell me so that i can guide you further.
Ashwin