i move the cup near it. i haven't even tried to use the medium if i'm having this much trouble with the small.
also, on the side - i keep pinching myself when i try to run my finger along the edge/front/back of the cup once it's in to check, is that normal??
you might have better luck if you change which way the cup faces as well... if the fold is usually in the front, try turning the cup so it's in the back.
i think i finally managed to get it to open up last night! but it's not a round or even oval shape. it's still got the slight c-shape 