Note: This is also applicable to Interset 4.x.
When attempting to load the Investigator UI (e.g. http://<REPORTING_SERVER>), you may receive an error page with a message of "ERR_CONNECTION_REFUSED". This is generally caused by one, or both, of the two items below:
nginx is not running
Confirm status of the nginx service and start if needed using the sudo service nginx status command.
nginx handles all web traffic, and various internal requests in the product, that communicate with the server. If this service is not running, you will be unable to load the Reporting UI.
Traffic is being blocked by a firewall
Confirm that iptables rules have been modified to permit Interset traffic as per Appendix D in the Deployment Guide.
iptables is a firewall built into RHEL and CentOS Linux distributions, and is running by default. Without modifying the firewall rules as outlined in Appendix D, or stopping the iptables service, it will not be possible to access the necessary ports on the Reporting server to access the UI.