Set-VM -hardwareversion v13 fails with "the operation is not supported on the object"

We're behind some firewalls that make Nuget impossible. We were able to get PowerCLI 11.2.0 installed by an offline process, coping the folders to the modules directory, and that works well for almost everything, and initially when I tested it, it worked (was able to convert a v10 VM to v13).

But ever since that first test, it consistently fails. I saw a post someone had made:

PowerCLI - upgrade VM hardware from v10 to v13 failing

Solved everything this way:

1. Uninstalled PowerCLI from ADD/Remove programs

2. executed Install-Module VMware.PowerCLI

3. Imported: VMware.PowerCLI instead of VMware.*.Core

     import-moduel PowerCLI

I'm not sure if that is relevant to my issue, as we already have a new PowerCLI that should work? The VM is on a 6.5 host. Is there an OS restriction? (it is a 2008 R2 server, but it has failed on 2012 too) VMTools is current.