Sometimes, after upgrade Magento, and introducing a new template, You may not see it.
Because each product can have a changed template to ‘default/default’.
1) just save product in admin panel
2) write simple SQL script, updating product attribute ‘custom_design’ to null or set it blank
3) write php code, using Magento API, upgrading ‘custom_design’ attribute
4) (best one) choose update attributes, for all products in admin panel -> manage products, and set Custom design to first option “Please select”
That’s all for today 🙂