Hi giussepeverdi,
Don’t Know.
But very Interesting: “2.6.2 this version worked well for me”.
I had some trouble too in Maya 2019.2 ( See post below )
If I may ask, Windows or macOS?
(The installer on macOS, when finished, asks Keep or Trash, if Keep,You have a backup of the installer, and you can uninstall the ProRender too)