this is windows issue in 2012 some time in evaluation copy
I have managed to resolve it by performing the following;
1. Backed up existing vPostGres database.
2. Uninstalling vCenter Server on Windows Server 2016 . I didnt export certificates.
3. Re-installing vCenter Server with an existing external platform service controller (appliance based)
4. After successful installation, stopped vpxd and content library services, restored vPostGres database
5. Started vpxd and content-library services. Then, i could access flash and HTML5 based web client with same set of ESXi hosts. I had to disable and enable HA before adding hosts back into the