Pro Sites: Upgrade from one paid level to higher

I have three Pro Sites levels, all paid levels. I have a client who wants to upgrade from her level to a higher one. I don't see how this can be done. The instructions say this:

Subscription Selection

With Pro Sites configured, users will be able to upgrade their site to a Pro level via the Pro Sites sidebar option in their Admin dashboard or by clicking the Pro Sites link in the Admin bar. Pro Sites displays a table of subscriptions with the site's current level highlighted for easy reference.

But I see neither a "Pro Sites sidebar option" nor a "Pro Sites link in the Admin bar." Below are images when I'm logged into one of my client sites as a regular site administrator.