The dough is too firm.
Add a little more liquid.
The food does not rise sufficiently in the oven.
Add a little more liquid.
Reduce the proofing temperature.
Add the moisture much earlier on in the cooking process. Ideally, you should preheat the oven before placing the food inside and then release a burst of steam straight away (if your oven supports this function).
Add a little more yeast to make the food rise better. For bread mixtures that are close to their expiration date, add additional dry yeast.