Use the Reset All Certificates option if you want to replace all existing vCenter certificates with certificates that are signed by VMCA.

When you use this option, you overwrite all custom certificates that are currently in VECS.

On a Platform Services Controller node, vSphere Certificate Manager can regenerate the root certificate and replace the machine SSL certificate and the machine solution user certificate.

On a management node, vSphere Certificate Manager can replace the machine SSL certificate and all solution user certificates.

In an embedded deployment, vSphere Certificate Manager can replace all certificates.

Which certificates are replaced depends on which options you select.