Check you have OpenGL installed.

The OpenGL driver on your Windows PC is what PhotoToMesh uses to create the 3D views of your STL and DXF files. The best way to check that PhotoToMesh works on your PC is to download and try the demo. If that works then so will the full version.

A further test is to download and run GLversion_debug.exe. Get it from this page:

Topicscape GL Version Test Program
(There is a download button half way down the page)

When you are running PhotoToMesh you can see what driver version and graphics vendor you are using by right clicking on the 3D image and selecting "OGL Driver Data..." from the menu which pops up:

The printing of a star shaped lithophane