Need help printing a simple empty-box-like object

[fred_dot_u]

The STL file was very helpful. When I imported it with Meshmixer, the entire cube was presented as individual components. For example, the square dot at the bottom of the question marks were not "glued" to the box face. This applied to all of the components. The repair facility in Meshmixer deleted most of them, destroying the model in the process. Microsoft 3DBuilder imported the model as expected and informed me of the errors, then fixed them correctly. I'm not sure why Blender breaks models in this manner but it's not the first time I've run into it. If you have Windows 10 or above, you may be able to import and repair your creations in the future. If not, I'm happy to assist.