Can you try accessing web client using https://<vSphere WebClient_ServerName>:9443 or https://<IP_Address_WebClient>:9443 (not the loopback address). For this to work you need to ensure that your Web Client Server Name and IP are registered in DNS (both Forward lookup and Reverse Lookup Zones). So you can validate if your Web Client name is resolvable by running at command prompt:
C:\.....>\nslookup <vSphere WebClient_ServerName> - This output should give you the IP Address of the Web Client Server
or nslookup <IP_Address_WebClient> - The output of this should give you the name of the Webclient Server.
Thanks