This was not happening to me on win7 but on win10 I'm constantly having issues of s3d not wanting to start (opens the main window and then it stays white and app is not responding) ... I clean the registry key and it works (all settings lost) .. works for few days, then stop again .. etc etc..
today, the same thing happened to me with prusa slicer 2.0 ... (not same but similar, it opened menus and interface but when it was about to init the 3d view it stopped and became unresponsive), but, I noticed similarity, both prusa slicer 2 and simplify3d were opening on left screen (negative X !!! ) so I assumed it had to do something with that, and as I remembered that developer mentioned that "geometry" key in the registry is "position of windows" I deleted only that key and dang s3d opened properly on the main screen (positive X) ... so, the issue I was fighting is - I move s3d to the left monitor, close it, it tries to start on the left monitor (negative X) and cannot.
PLEASE FIX !!! should be simple .. if there's an issue of starting on negative X (I'm now finding more and more 3d apps that have same issue, looks like it might have to do with Qt) just reset it back to main screen but start