"Unexpected error. Check your network connection or view Director Server event logs for further information"  under Trends > Failures > Connection.

The other options within Failures Tab (Desktop OS Machines and Server OS machines does not give the error) and all other tabs such as Sessions, Logon Performance, Load Evaluator Index does not give any error.

In some conditions, the error only occur for a specific time range.

Note: This issue is applicable to Citrix Director Server versions 7.13 and 7.14.

This (LC7755) has been fixed in version 7.15. Refer to Citrix Documentation - Fixed issues.

Problem Cause

This issue happens if "FailureId" in MonitorData.Session table and "DesktopGroupId" in MonitorData.Machine table (related machine of session) contains "NULL".