Then you have not cooked it long enough. It should sound 'hollow' when you tap it , if not then it needs longer in the oven. What oven temp are you using? Bread needs a hot oven 200 to 220 deg C.
as above and I always ensure that there is a gram more yeast than low sodium salt. I cook my 512 gram flour loaf recipe for nearly an hour on 220C if that helps.