No objects showing in Dimension

Hi. This is my first post as a CC member.
I have installed Dimension as I really want to do some packaging designs and to try and create realistic looking 3D models for product design. No matter how many times I have tried, I cannot get any objects at all to actually appear in the window. I'm pretty computer savvy and I use alot of Adobe programmes already. When I click an object from the left hand side menu, it says loading but then all I get is the red, green and blue arrows in the window but no object. I have tried placing so many things into the window but absolutely nothing shows up. In the scene window on the right it labels all the objects I've apparently placed but I just can't see them.
I've watched the tutorials several times and looked on youtube and asked in my graphic design groups but nothing.
Please can anyone shed any light on what I am doing wrong?