Hi,

Your code's only check _SERVER['HTTPS'] On

But behind a RProxy, your code should check
[HTTP_X_FORWARDED_PROTO] => https
[HTTP_X_FORWARDED_SSL] => on
[HTTP_X_URL_SCHEME] => https

This could troubleshoot probleme with Ajax, such as "Supports concrete5 request URLs", wich is just an ajax call being refused because called with http ... (thus it taks a 30x in return which block the verification)

Blocked load of mixed active content « http://**DOMAIN**/index.php/install/web_precondition/request_urls/20?_=1520771956989 »[En savoir plus] jquery.js:5:25679

Thanks for giving help to modify the code to force accept HTTPS, while called by http