Program gets suspended while running in background

A program was working until I got a notification saying that the program was running in the background, and if it was necessary or not. I stupidly clicked the button to force quit the program, and now every time I de-focus the window that the program is running in, it gets suspended. It was suspended by the Portal application. I cannot seem to get it back. Please tell me what I need to do in order to solve this problem.