I think they recently made a cut off number for circles, I'm not sure why that is.
Kim, when you say you don't have anyone in your circle, I believe it's because you have not added anyone to yours. People can add you to their circle, but if you don't reciprocate, which you are not obligated to, then you won't have them in yours. Does that make sense? The number of circles you are in and how many people are in your circle can differ. Hope this helps.