VCF 5.x
The precheck status depends on the health of the target vCenter. SDDC displays what the backend serves without modification.
(i) From the SDDC command line as root attempt an SSH connection as follows: ssh root@<vCenter_FQDN>
(ii) Try a connection using strict key checks: ssh -o StrictHostKeyChecking=yes root@<vCenter_FQDN>