try downloading from here:
downloading and installation>software Download links>i need to redownload my product>Autodesk Suites>Building Design Suite
I am experiencing the same communication error when I try to download the free trial version. I followed the steps with the virtual agent, but when I click on Revit Architecture 2014, it prompts me for my subscription number which I don't have since it's the free trial. I have been trying to dowload this for several days and very frustrated at this point.