DasAgentUnavailableEvent
Summary
vCenter Server cannot contact any primary host in a HA cluster.
Causes
vCenter Server lost contact to all primary nodes in the connected state. Further attempts to configure HA on the host will fail until a DasAgentFoundEvent is logged or unless this host is the first node to be configured.
Resolutions
For resolution steps, refer to this VMware KB article.
External
Refer to the online vSphere Availability Guide for further guidance.