Issue with BackgroundSubtractorMOG2

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I'm having an issue with the BackgroundSubtractorMOG2 where foreground detection is just not happening at all.

backgroundFrame = 5;
while(true)
{
    if(backgroundFrame>0)
    {
        bg.operator ()(frame,fore,.01);
        backgroundFrame--;
    }
    else
    {
        bg.operator()(frame,fore,0);
    }
    imshow("MyFrame", fore);
}

the idea is that the background is collected using 5 frames, and then subsequent frames will not be calculated as part of the background. This is done by changing the learningRate variable from .01 to 0 after 5 iterations. However, after 5 iterations, fore shows up as a completely black screen. From my understanding, it should show any deviance of current frames from the background as white. Does anybody have past experience in this matter?

Thanks!