Conversion of existing VVF to VCF can potentially fail due to incorrect DNS entries caused by DNS server issues during bring up. This will cause the conversion to fail with a similar error,
VCF Installer: /var/log/vmware/vcf/domainmanager/domainmanager.log"org.springframework.web.client.ResourceAccessException: I/O error on GET request for "https://<vcf-ops-hostname>/casa/sysadmin/slice/vmware/buildinfo": Certificate for <vcf-ops-hostname> doesn't match any of the subject alternative names: [localhost, vcf-ops-shortname]"
VMware Cloud Foundation
Before upgrading VCF Ops, update the correct hostname using steps in KB, "How to change a node hostname in Aria Operations"
Once hostnames are correctly set, proceed with the VCF Ops upgrade.