I've pulled the STL file into Meshmixer (free) and immediately noted there are modules modeled in the box. Unless you want those printed, you'll want to pull them from the file sent to print. Also, the pillar in the center and the inside floor of the box have reversed normals. This means they are "inside out" and will cause print problems. There is also a narrow strip away from the cover and box that has reversed normals as well.

I didn't try to remove the modeled modules inside the box.

I can't advise you of the best way to put the normals back to normal, as I'm not a TurboCAD user.