AppFlow (aka Insight) has been enabled for the VServer and Services. Enabled Web Insights on NetScaler MAS no data is displayed.
Firewall port UDP 4739 is allowed from the NetScaler NSIP/SNIP to the MAS appliance.
ULFD was disabled and server was removed.This is due to a known issue. As the removing of ULFD is not clean in older versions we need to reboot the NetScaler after disabling and removing the ULFD server.
Citrix Documentation - Web Insight
Citrix ADM version 12.1 build 49.37 and above has self-service diagnostics for Analytics which is used to identify the license and configuration issues on the managed instances which could lead to no data being captured. The self-service diagnostics helps you to identify and troubleshoot the issues faster. For more information refer to Citrix Documentation - Self-service diagnostics for Analytics.