The VMware vSphere web client requires Flash 11.5. I’ve noticed some issues with certain versions of Chrome and IE11 on Windows 2012 R2 not being able to open the web client due to either a missing or incorrect Flash version. Luckily, enabling the built in flash player for IE11 is an easy process.
From an elevated powershell prompt, run the following command
Once this is complete, reboot the server. When the server comes back up, good practice is to patch the version of Flash Internet Explorer will use via Windows Update, but the vSphere Web Client should now work.