This support documentation needs to be fully reviewed and updated.
https://help.sansar.com/hc/en-us/articles/115002888226#blender%fbx%export
There are specific instructions regarding Tangent / Binormal being a requirement which I have been told is no longer the case. Also note that the attached screen shot includes the check box for Tangent / Binormal being checked. This screen shot should be recreated.
There may also be other errors in this document that have resulted from updates to Sansar.