Fix a Drupal migration that does not work on the new server (redirection fails / cookies)

We have a small website developed with Drupal 7 more than 6 years ago. It works currently like a charm on a Rackspace server (MySQL version 5.5.61, Webmin Version 1.930 on [login to view URL] (CentOS Linux 6.10) PHP Version 5.4.45). For reasons of cost we have to migrate to a cheaper host and we have now a server on CentOS inux 7, Php 5.4. Obviously the architecture is quite different (instead of everything under /home/my-website, this is now under var/www/vhosts/my-website). Once migrated correctly and [login to view URL] updated with the new path, we can login to the admin panel, we can see the different pages as a normal visitor... However the developers have used a "hook" apparently to manage the redirection of the different sections, and that does not work. We have the standard message: "The page isn’t redirecting properly Firefox has detected that the server is redirecting the request for this address in a way that will never complete. This problem can sometimes be caused by disabling or refusing to accept cookies." It would be a directory path, a way of handling cookies... or else, we have no idea. Maybe the function to handle the redirection needs to be amended (we doubt it as it works currently) but in any case we need help. Here is the copy of the guide explaining what does not work: ---------------------------------------------------------------------------------------------- One of the main feature of the site is that the user can select a country on the top block listing all countries. Once this choice is done he main remains in that country while browsing the website. A long term cookie is sent to the user so that he may get back that same country when coming back on the website on an url which does not enforce a country. If a country is present in the website url then that country became the current navigation country. When the user choose a country in the select form an ajax request is done, the website retains the chosen country for the user session and in the json response some orders are given to perform a page redirection. This way the new url will contain the country chosen by the user. This is not always working, as the ajax query needs js support, or a fast fast js support which is not always present on mobile tools for example. So the user can also submit his choice with the button near the country selector. This form submission will have the same effect as the ajax query (url redirection).