uh oh, that's not good - especially as I can't really find a reason why that might be. Just to confirm: You are selecting the "Push your limits (stomach will grow)" option, and have the funds and/or fat to have one full uninterrupted day of downtime? Only the push your limits option will cause your stomach to grow, and at minimum you must be able to get through one day of downtime (I added that check as anti-cheese, because otherwise you'd be able to get a full stuffing's worth of expansion without the funds to afford even a single bite of food xP).
Otherwise I'm stumped. You could send me your save file if you'd like (by using save to disk), but I'm not sure if that'd help me uncover anything.