I had the plugin working, with one level, but when I added others, the protected content is no longer protected.
A little about my setup:
There are 5 levels, the all cost the same, they access the same two protected pages. (The difference among them is unrelated to content on the site.) Everyone is set to Indefinite Mode (pay one time only)
So I finally got the Paypal working, then I realized that the content was no longer being protected.
I have tried the obvious: make sure I'm not logged in. I have checked access levels. The levels have the same permissions, and the Visitor has inverse of them (prohibited in the Negative filter). I have made sure I have a gateway chosen.
I have tried making the subscription plans Private. And gone over all the options. It was working earlier today and I didn't change anything that I know of.