Upgrade 4 to 5 after upgrading to 6

We have 4 seats of Rhino 4, bought 4 upgrade seats to 5, 4 upgrade seats to 6. Two of the upgrades to 5 were never used, i.e. those workstations got a 6 upgrade from 4. Now I would like to install the version 5, but I am getting the error “license already upgraded”, which I assume it means to 6. Is something messed up on my end or does McNeel not allow installation of 5 after an upgrade to 6, which would be messed up policy-wise too, I suppose. It wouldn’t be a big deal if there wasn’t so much file version compatibility issues. Even clipboard doesn’t seem to work more than one version apart…

This is not something for the Forums.
Please contact the regional McNeel Sales office for help with this.
It looks like maybe you’re in Canada so that’s Seattle.
206.545.7000. We’re open until 5p PDT, and 2.5 hours more today.