If the self-assigned VMware esxi 6.0 SSL Certificate expired on a Host and displaying a warning or an error in vCenter on the Host, you will need to renew that SSL Certificate.
The certificate can’t be renewed through the VMware vSphere client, but can be renewed via the Web Client but unfortunately that would require Adobe Flash to work, and Adobe Flash has been deprecated and unavailable to download unless you had an old browser with flash installed and you never removed flash from it.
We had this issue last week. We found another way to renew that certificate and that is by going to vSphere client, right-clicking on the Host and disconnecting it, wait a few seconds then choose to reconnect it. By reconnecting the Host, that will automatically renew that ssl Certificate.
Do at your own risk. We take no responsibility for anything that could go wrong.