Activating IPS in a site policy causes problem

Hello,

When the IPS is activated in the firewall site policy, this site becomes unreachable from the outside (from the internet).

The error below is displayed when trying to access this site;

This site can't be reached 

(the site) Unexpectedly closed the connetion 

When the IPS is desactivated, the site becomes accessible again
The problem occurs only for sites in https,  It doesn't affect the sites that are in http even if the IPS is activated for those sites.

I would like to know why the IPS blocks access to sites that are accessible in https

The firewall Inspection mode : Proxy-based

I hope you will help me, thank you in advance