Welcome to Skyline communities.
As per the error that you have shared, We understand that Skyline is not able to receive the certificate from vCenter.
1. Make sure the ports (443 and 7444) are open and connectable between vCenter/Hosts and Skyline on the network.
2. If there is a firewall make sure there is no SSL filtering for Skyline
3. You could try to connect with vCenter using the curl command below, Open the console of Skyline VM
curl -v https://vcenterfqdn:443
curl -v https://vcenterfqdn:7444
4. You could also check on which port vCenter is configured from the file vpxd.cfg
Yup, that was it!
Thanks a bunch!