This version of vCenter Server does not support Deploy OVF Template using this version of vSphere Web Client. To Deploy OVF Template, login with version 6.5.0.0 of vSphere Web Client.
Environment
VMware vCenter Server Appliance 6.5.x
Cause
This issue occurs due to an inconsistency in the SSO token signer certificate for environments upgraded from 5.1 or earlier.
Resolution
This issue is resolved in VMware vCenter Server Appliance 6.5 b, available at VMware Downloads.
Workaround: To work around this issue, deploy OVF files using the command line. For more information, see the OVF Tool Documentation.