In the current version of Trimble 3D Warehouse, you should first click on the image of a model, then click on Download red button to choose KMZ or Collada file format that is supported by Sweet Home 3D.

Said an other way:
Don't click on the symbol shown at the bottom left of model images:
NO

but click on model images themselves, then click on Download button and choose a file format supported by Sweet Home 3D:
YES