ESXi host displaying error: "vSphere HA agent on this host could not reach isolation address <IP Address>'" in the vCenter server

Products

• VMware vSphere ESXi

Issue/Introduction

• In the vCenter user interface, in the Hosts and Clusters view, with the ESXi host selected, you see the message "vSphere HA agent on this host could not reach isolation address <IP Address>

Environment

• VMware vSphere ESXi 7.0
• VMware vSphere ESXi 8.0

Cause

• The ESXi host is unable to establish network connectivity to the defined isolation address indicated in the error message

Resolution

• Verify network connectivity is possible from the host.  It may be necessary to check connectivity to the isolation address from a specific VMkernel Adapter.  This may vary from in individual customer environments   
• From host CLI confirm network Connectivity to the host from VMK adapter
  • vmkping -I vmk<#> <Isolation_Address>

Additional Information

• For more information on using CLI command: vmkping, please reference the following article: Troubleshooting network and TCP/UDP port connectivity issues on Hosts
• After confirming network connectivity is possible to the Isolation address from the hosts vmk interface and the error message is still presenting on the ESXi host, please proceed with verifying: vSphere HA agent on this host could not reach isolation address '#.#.#.#', reported on ESXi host