Most often, this is because either the ports between the vCD cells and the ESXi hosts are not open (Ports 902/903) or the Public IP Address for the console proxy is set incorrectly in the admin interface or certificate errors have occurred.
Since it is the same IP address as for your portal, you can use the same URL for the public IP address as for the HTTP and REST API endpoint, the complete certificate chain must also be configured correctly and the certificate for your vCD endpoints must either be imported into the client or use signed certificates, so that they're always trusted.