Windows 10 may block the older security protocols used by vSphere 5.5. Some users resolve this by using tools like IIS Crypto to re-enable older hashes like MD5 or SHA if your environment is isolated and secure.
There are three primary ways to obtain the installer for version 5.5: From your ESXi Host (Recommended) Open a web browser and enter the IP address of your ESXi 5.5 host. A landing page will appear with a link titled "Download vSphere Client" vmware vsphere client 5.5 download windows 10 64 bit