Your model seems fine to me:
This is how I load my models myNode = (Node)assetManager.loadModel(“Models/myModel.j3o”);
If you converted the model to .j3o correctly you don’t have to set the material. It’s already set on the .j3o. Also, “TangentBinormalGenerator.generate(geom);” is not needed for this.
Also try triangulate your mesh before you export. Mesh->Faces->Triangulate Faces. Or just in edit mode with all faces selected press CTRL+ t.