phpBB + CleanTalk behind reverse proxy

Hi!

I’m running (for a customer) a phpBB site that used to be located behind a dedicated IP address, but had to be moved to a shared IP address.

After moving from dedicated to shared IP, logging into phpBB became impossible. When ever trying to log in, the FORM_INVALID error is triggered.

There’s a reverse Nginx proxy handling traffic to the shared IP, and a separate local Nginx instance handing the traffic coming in through the proxy.

I’m using the Nginx Real IP module to replace the internal IP of the proxy server by the original IP of the client. In other words, everything the back-end (including php-fpm) sees is the original client IP.

Do you have any idea how to get around this issue?