Check Foglight Management Server Logs and find this message:
WARN [TimeDriven_Worker-2] com.quest.nitro.service.rule.rule.Rule - Failed to evaluate expression #readLatency# in rule: VMW Datastore Read Latency
com.quest.nitro.service.sl.interfaces.scripting.ScriptUndefinedObservationException: undefined observation (present but empty observed data for topology object 436bbdf7-7658-4cc5-be79-4147843cc264) in query: readLatency
This is a known defect request in vFoglight referenced by Quest Tracking ID VFOG-10439.
Defect request VFOG-10439 has been submitted to Development for a fix in a future release. Please check the release notes of latest software to determine which bug fixes have been included in this release.
This issue gets fixed on VMware 5.6.16 which comes on Foglight for Virtualization 8.3.
The latest version of Foglight can be downloaded at: