In case you do not have vegetable broth powder, then you can simply add vegetable stock or water. In that case, you may have to add a little extra corn flour (maybe 1 tsp more).
In case you are making the soup in the regular way and not in the soup maker, you might have to strain the corn puree through a fine mesh after you have blended it. Also you will need to boil it for longer period, in case the quality of the corn is not good and has dried out. For regular sweet corn, just boiling for 5 – 10 minutes works fine or a couple of whistles in the pressure cooker.