Scattering Model Doesn't Compute

Hello,
I'm trying to model the scattering effects of light off of a thin box. I used the model example "Optical Scattering Off a Gold Nanosphere" as a reference model. " I've tried a few approaches when modeling the system, and I keep getting the error "Undefined value found - Detail: NaN or Inf found when solving linear system using SOR. - Feature: Stationary Solver 1 (sol3/s1)". I don't know where exactly the undefined value is coming from. How can I avoid/fix this error?

Thanks,
Daniel Frantz