I would return the incubator.. That will not help her lay eggs (this is why you make a dig box..
The incubator is only to provide proper artificial environment to hatch the eggs presuming they are fertile. This costs time and money it costs more to produce them than their market value (which is why pet store iguanas are farm bred on foreign soil they are extremely cheap for them this way). Unless you want dozens of other iguanas that will be hard as hell to re-home then I would simply freeze the eggs and toss them. They can hold sperm for many months.. So if she has been around your other iguana its possible they could be fertile.