Hi Angelo!

Thanks for posting on our forums. It looks like the main issue is that your lens doesn't look it is coming to focus at the image plane. The way that the Image Simulation feature works is that it will look a certain grid of PSF points (either Spot Diagrams with 'Aberrations' = 'Geometric' or PSF results with 'Aberrations' = 'Diffraction') over your field of view. If your PSF Grid is poorly performing, then the Image Simulation tool will have issues getting results. Here is the same issue with the Doublet sample file:

When the image plane is at a reasonable focus, the Image Simulation tool should start to display some rendered output:

I might also recommend using a non-zero value for your Field Height setting, since this input effectively defines the size of your input image file in object space. Below is a screenshot from our Help Files for Image Simulation at 'The Analyze Tab (sequential ui mode) > Image Quality Group > Extended Scene Analysis > Image Simulation':

 

Lastly, I would also highly recommend taking a look at https://support.zemax.com/hc/en-us/articles/1500005486701-How-to-simulate-high-resolution-images as well as https://support.zemax.com/hc/en-us/articles/1500005489601-Simulating-image-quality-in-OpticStudio-webinar for some additional resources and demonstrations on using Image Simulation.

Let us know how these thoughts work out for you!

~ Angel