When I login to vsphere6 web client to one virtualcenter, I see all 3 of my virtual centers
but when i login from the thick client, I only see one.
any idea? Do I have to manually configure linked mode on the thick client?
please see above documentation link, as it is mentioned. Linked mode is only supported by vSphere Web Client.
The vSphere Client does not support Enhanced Linked Mode.
I hope it will help.
in short, Enhanced Linked mode in not supported by vSphere client (which you are referring as Thick Client, aka vi client or C# based client)
I think Jagadish is referring term Thick Client in the context of actual Desktop PC, where you have web browser available so you can use Web Client on it.