I am having the same problems as nicola.colaninno. I installed SNAP 6.0 on a Windows 10 operating system. I did not download the standalone version of Sen2Cor or the Anacona one, I just followed all the steps described above. I do have something from SNAP in my user variables of the environment variables (C:\Program Files\snap\bin), but not from Sen2Cor. However, every time I try to run Sen2Cor on images that I downloaded from https://scihub.copernicus.eu/dhus/#/home, I get an empty AUX_DATA and an empty DATASTRIP file within seconds. I am not very good with computers so this plugin use via SNAP seemed perfect for me, but I just cannot manage it to work properly. Does anyone have suggestions on how to deal with it, or on another way of using Sen2Cor?