We had an ig , that after spay and removal of ovarian cancer , would not eat . She went about 6 weeks with no food and then one day I noticed she was eating dirt from the crack on the floor just inside the from door. Oddest thing I had ever seen...I ended up syringe feeding her with fruity baby food, mixed with critical care which your vet may have available but its cheaper on amazon. It was s till several weeks before she ate on her own and for a while the only thing she would only east grapes.
Iguanas are amazing resilient animals and can go months with little to know food if they were healthy to begin with.
Surgry seems to mess up my girls that have been spayed but none had ever been as stubborn as she was.