Hello antonioceravolo,

In your case problem is that you try to use not secure server for Jot messenger module which is installed on secure site.  I described this problem here https://una.io/page/view-discussion?id=1815

Problems may occur if you install Jot Server on server without certificate and then try to use link from this server on https (secure) sites, in this case all requests from https sites will be blocked by your browser, because in most cases browsers don't allow to load not secure content (http) to secure sites (https).

Example: if Jot messenger installed on https://mysite.com and server on http://my.jotserver.com, it will not work because browser will block not secure requests, 

but it will work if: 

1) Site on https://mysite.com and server on https://my.jotserver.com

2) Site on http://mysite.com and server on https://my.jotserver.com

3) Site on http://mysite.com and server on http://my.jotserver.com