You should be able to call your VAR to deactivate the license that is tied up..
Have you checked with your VAR? They may be able to deactivate or at least offer advice.
Have you checked the Customer Portal > CAD Admin Dashboard? (I have no idea if that gives access but worth checking)
There are ways to reset your server license but you will have to also make certain that this end user also forces the license off their client machine as well lest you have a license in two places at once. I don't see that you have given us a call to discuss this yet but if you want assistance please give us a ring (888.559.6167).