vSphere HA Agent on the host is invalid. Examine the host to determine if it has been compromised.
There is an issue with vSphere High Availability configuration for this host. Review the event description for detail on the cause.
See VMware online documents such as Troubleshooting VMware High Availability and the vSphere Troubleshooting Guide to resolve HA issues.
Refer to the online vSphere Availability Guide for further guidance.