Disclaimer: I have not used shape ways too much yet, so I am not sure of the specifics, so it is possible I am completely off.
This is actually a point of confusion common to people when they first move from one package to another.
3Ds Max uses what is called a Z up world. That is to say that Z is up and down. Other packages use a Y up system, so that the Y axis represents up and down. This can cause problems when moving models between packages because the model doesn't know which way is up; they only know their x, y and z coordinates. This can commonly result in the object.
What I would suggest, in this instance, is that shape ways model viewer uses a Y up system. After a quick google, I have confirmed that Max has a 'Flip YZ-axis option.' Have a play with that, and see what results you get when importing your models.
EDIT: I've just uploaded a test model, and it seems that shape ways uses a Y down (positive Y value is down) system.