RepV1.5.6 + Slic3r1.2.9

how can i upgrade Slic3r1.2.9 (from on RepV1.5.6?

I get always this error:

You have to allow download of the image if you want to show us.

Still forbidden. You need to publish the file or put it in the public folder of dropbox.

Not sure what the forum hosting platform is doing with inserted images, but @nmaia1's second link does work (for me anyway) with a cut/paste:

Ok, could open image over the link published. Didn't understand a word. What is the error saying in english?

You could try starting slic3r directly and see if it runs.