Answer by victor

You are completely right. The file is the portal-ext.properties:

/opt/bitnami/apache-tomcat/webapps/ROOT/WEB-INF/classes/portal-ext.properties

and the lines to be added are:

atom.servlet.hosts.allowed=127.0.0.1, YOUR_IP
atom.servlet.https.required=false

It works for me. I hope it helps you.

Regards.

EDITED: Reference links

General properties

http://www.liferay.com/es/documentation/liferay-portal/6.1/user-guide/-/ai/configuring-liferay-s-properties

Atom properties

http://www.liferay.com/es/documentation/liferay-portal/6.1/user-guide/-/ai/atom-servlet