1. Was the virtual machine part of standard switch or distributed switch ?
2. Was virtual machine able to ping other virtual machine on the same host and same port group ( when it was restarted after the HA failure ) ?
3. If yes, then it could be something upstream to the ESXi . If you have multiple network adapter cards connected to the vswitch or distributed switch and the interfaces connected to the vmnic don't have identical configuration ( some vlan missing ) then you can encounter the same issue . It can also be possible , if MAC address table not synced properly on the physical switch .
4. You can check the port group configuration on both the host and make sure they can identical as well.
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Regards,
UJ