Premium Plugins Auto-Activation not consistently working

Hi: I am using Pro Sites to create two paid levels for my MultiSite blogs; the higher level also includes MarketPress among its Premium Plugins. Because we expect our users to be not particularly tech savvy, I have taken the Plugins page out of our user dashboards and am relying entirely on the Auto-Activate feature of Pro Sites Premium Plugins to activate the correct plugins on the correct levels.

Problem is, it's not consistently working. It is auto-activating some plugins but not others - and MarketPress is one that isn't being activated, and that's a huge problem for us. I have tried network-activating these plugins, and then they all work; I have also re-inserted the Plugins page on the users' dashboards, and it correctly lists the plugin status for every plugin - i.e., if a plugin for a certain level won't auto-activate, it is listed as not activated on the Plugins page.

Even worse, one of my plugins will auto-activate correctly on the lower paid level but *not* on the higher level . What's going on here? We're launching in three weeks and I *really* need this to work correctly. Anybody have any ideas? My thanks in advance --