With the NetScaler Release 12.0 Build 51.24, NetScaler admin can view the status of connectivity between NetScaler's SNIP address and Appflow Collector by checking new information called State

NetScaler's SNIP address is used to detect network reachability between NetScaler and AppFlow collector. If there is either communication problem or there is no SNIP address available to send monitor probes (ICMP is used for probing), State of AppFlow collector will show as DOWN.

Note that for ADM Analytics to work properly, NetScaler should be able to reach ADM through SNIP. Otherwise NetScaler will not send any AppFlow records and this will lead to no data being shown on ADM.

Verifying Status of Connectivity Between NetScaler SNIP and AppFlow Collector

NetScaler CLI

This can be checked via NetScaler CLI using following command: "show appflow collector" 
This information is listed under State as shown in the following example:

> show appflow collector
1)      Name: af_collector_x.x.x.181
        IPv4 address: x.xx.181
        Port: 4739
        Netprofile:
        Transport: ipfix
        State: DOWN
 Done
>

NetScaler GUI

Citrix Documentation: Getting Started with ADM - Review the System Requirements - Ports
CTX202528 - NetScaler Insight Center Does Not Display Data