Infinite redirects from HTTPS to HTTP on brand new server

[yarekc]

I installed Prestashop for first time on new servers (I even tried 3 different servers: debian10, php7.4, apache2, https with letsencrypt, server up to date)

Installation: no issues at all. I do install it from 
https://new.bigsquash.com

When I enter the store, I got infinite redirection and I got redirected from https to... http ans so on: until infinite error.

I got the same issue from the admin panel where JS are trying to be downloaded from http:// and not https://

I never indicated any HTTP url and ALL my url have https - including the apache rules generated by letsecrypt. (I even disable http in apache)

(I also tried to setup cloudflare: Same issue.)

 

I created a test.php file: 

https://new.bigsquash.com/test.php 

And everything works fine also my admin panel does not generate redirections: https://new.bigsquash.com/admin/

But I got MIXED HTTP and HTTPS calls such as: 
 The page was loaded over HTTPS, but requested an insecure XMLHttpRequest endpoint 'http://new.bigsquash.com/admin466uztgtb/index.php?controller=AdminGamification&token=xxxx'. This request has been blocked; the content must be served over HTTPS.
 

 

So why Prestashop is using HTTP:// whereas I never use http and everything is well configured on my server.

 

- I emptied cache, enabled debugger, disabled cache. 

I just cannot understand why prestashop is mixing http and https. 

 

For me it looks like prestashop cannot be correctly installed on a sub domain

Edited October 3, 2021 by yarekc
more details added (see edit history)