Updating Atelier - Sites not found & Proxy Authentication

Hello everyone :-)

I would like to update Atelier from version 1.0.262 to the 1.3 one. So I clicked on Help --> Check for updates, and I get these first error messages:

"No updates were found in available software sites."

"Some sites could not be found. See the error log for more detail." etc. cf picture below talking about Proxy Authentication.

So I checked those available software sites (tried until now) and also the proxy settings that I am used to work with:

Then I changed the "Active Provider" from Native to Manual with the proxy settings got from a system administrator :

So here is the result of a new try of "Check for updates": "Unable to read repository at {any site name}/content.xml. The target server failed to respond" :

Do you know where it could come from ?

In any case it could be useful, here is a last picture of details about my current version of Atelier:

Best regards,

Mathieu