Yea, you probably want supports there. Why don't you post the factory file? There are several software settings that could easily have prevented S3D from putting support there if you have them wrong
Your 3D model is a completely solid part. You have set the infill percentage to zero, which means the software will only print the outer-most perimeters, and will not place any material on the inside of the part. You posted a picture of the inside of the part asking why there wasn't support there. If you want material there, then you need to use an infill percentage greater than 0%. It isn't going to place support inside the interior of your part, as that wouldn't make any sense
there are no internal areas of this getting support. everything pictured is an external area. move your layer slider down or use the cross section tool and look closely. that area with infill is not a solid part of the model and is external.
yes i know. look closely at the model. that is not internal.just because you dont have access to it when its done and printed doesnt mean its internal. use the cross section tool and lower it down near the bottom where that feature starts. its open at the bottom.
You should probably also not be using 4mm supports for a model that is only about 20mm wide with many features less than 2mm in size. Decrease your support pillar resolution to 1mm and I bet it will look much better.