For me the key to getting a ginger bug nice and bubbly has been to stir, stir, stir. Pretty much every time I go into the kitchen I stir it vigorously. I've also found that the the wider the mouth of the bowl the more likely I am to get quick activity. Even then it can take 4-5 days, depending on the temp. Did you stir often? What type of a dish did you have it in?