Why won't my mousse foam?

If your mousse isn't foaming, it could be due to several factors. First, make sure your cream is cold and has enough fat content (at least 36%) for whipping. Additionally, overmixing or undermixing the ingredients can prevent proper aeration; be careful to fold gently to maintain airiness. Lastly, ensure that there are no traces of fat or moisture in your mixing bowl or utensils, as these can hinder the whipping process.