Hi Patrick,
When you define a new product in the releases tab, the product can be
associated with one or more projects from your projects hierarchy. This
association is only for convenience, so that you can easily
select a product and quickly find all the items that are associated
with that product, allowing you to quickly assign those items to a
given release or milestone.
In order for those items to show up under release or milestones they have to be assigned 1) by dragging and dropping to the particular release 2) through multi-edit by selecting a release 3) or by editing the item and assigning to a release. Make sure the release field is available in your field templates.
Thanks,
Arash