I don't have a plan with VPN, but the K-base says it's under the user tab. If it's not there, have you checked to see if it's functionality has been moved into the Users > Manage users area? They re-arranged the panel a month or so ago, and put a lot of the stuff under the "manage" section of each area.
If you're sitll not finding it, you should contact support and then post your findings here for others. I would suspect that it's simply a glitch that it's not showing up for you.