I searched a little to find this issue and it seems others have experienced the same thing, but I'm not clear on the solution.
I'm using the v4.1.1 app for Android. I purchased a license last month. In the past couple of weeks, the app has notified me that it's time to buy. When I press "buy" (to see what would happen), that window goes away and it's back to normal.
The About screen confirms it Premium Features were unlocked on 8/19/14.
Do you have any suggestions that might clear this up?