Enabling Ack-Back is an option for Nagios/Icinga (explained below) along with Zabbix. In the following article, Nagios and Icinga can be used interchangeably.
Ack-Back™ is an optional feature that informs your Nagios instance when someone acknowledges its alerts in VictorOps. Note that you must be using the Nagios plugin to enable this feature.
Ack-Back is implemented as a Nagios service called “VictorOps Command Poll”. It retrieves acknowledgement commands from VictorOps for executing locally to Nagios. Enabling Ack-Back is simply a matter of enabling active checks of the VictorOps Command Poll service.
Find the service definition in the victorops.cfg file:
service_description VictorOps Command Poll
Set the value of the active_checks_enabled setting to 1 and reload Nagios.
Note: in some cases GCI/Admin access for the VictorOps user is required for ack-back to function properly.