The issue you are facing may stem from various factors, including but not limited to, server configuration, firewalls, or network restrictions. These factors could prevent your XLS Padlock application from properly exchanging information with your Apache server through the NGINX inverse proxy.
Therefore, I recommend reaching out to your server provider’s technical support team. They are best equipped to assist you in troubleshooting this issue, as they have direct access to your server configuration and can perform a more in-depth analysis of the problem.