Model not Watertight? What should I do?

I am trying to get a new model for the Dexterity hand watertight. I used the Meshmixer Repair Tool but still the model ist not watertight.

Now I am trying out the following tools:

  • Tools3D: the tool does not work, I made an account but then I cannot upload the file
  • MeshLab2016: Mac, Windows, Linux, I cannot find the repair tool option

  • MakePrintable: Cloud, looks promising, but I cannot find the download button

  • Freecad: Mac, Windows, Linux, pretty long process

and the Winner is Autodesk Netfabb. Its windows only but the with the extended repair Function i repaired the model easily.