I use: Multisites for Joomla! 1.5.x, 2.5.x, 3.0.x Version 1.3.65 - basic
Patches definition Version 1.3.60

I've got a slave site: www.artdeco.se and I'm gonna rebuild this site so I created a new "fresh slave site" with site ID: artdeco2 (the first has ID: artdeco). List of domain names: artdeco.se/2017 and www.artdeco.se/2017

When I go to artdeco.se/2017 I get "ERR_TOO_MANY_REDIRECTS" and the url is: artdeco.se/2017/installation/installatio...stallation/index.php

Any idea?

Based on the long URL with /installation repeated a large number of times, I am wondering if the /installation is a symbolic link or a physical directory as it is supposed to be.

Did you upgraded your environment from an older version of joomla to a more recent one.
If yes, then try removing the /installation directory present in the master and after redo a check patches to reinstall the /installation according to your current Joomla version.

Hi, thanks for your input. It doesn't work though

From the beginning:
All the domains master and slaves are behind Sucuri Firewall (for protection)
Joomla version: 3.7.0
JMS version: 1.3.65, patches version: 1.3.60

Master site: mettecosmetique.se
Slave site: artdeco.se
Slave site (new version): artdeco.se/artdeco_2017

I have created the directory "artdeco_2017" in public_html (root).

When I go to "artdeco.se/artdeco_2017/installation" I get error: "ERR_TOO_MANY_REDIRECTS" and the URL: artdeco.se/artdeco_2017/installation/ins...stallation/index.php

The way I see it the problem could be one or more of the following:
1. I must configure a new domain in Sucuri Firewall
2. I must update the patches, how do I do that?
3. Something is wrong with my configuration

The infinite loop that you describe seems related to the fact that inside the /installation directory you would have a symbolic link "installation" that would point to the parent.

If you would not have such "installation" symbolic link under the /installation directory then you would not have this loop.

You provided information concerning URL but what I would like to really know if the directory structure of the /installation directory and its content subdirectories and symbolic links.

1) I don't think so.
2) Go in the master website JMS / check patches menu. If some patches are missing, you have the "install" button to do that.
3) I don't know for the moment as we didn't really found the origin.

If you want that I have a look directly in your environment, this is still possible with our billable support that you can order at
www.jms2win.com/en/joomla-multisite?page...35&category_id=1