>>I had the same issue, I had to manually uninstall the current version (Took the backup first) then install the latest version saved the time and back into business. Looks like MSI issue.
Interesting. Having to uninstall a key component of vSphere in order to upgrade it! VMware's upgrades are getting more and more fraught with danger.
Did you uninstall just the SSO server and left the DB alone (mine is hosted on a separate SQL server)? Did you have to recreate users active directory identity sources etc. or was it just an uninstall and re-install?