If breadcrumbs are not showing on the product page in Magento 2, first check if they are enabled in the `catalog_product_view.xml` file. In most Magento themes, the `<referenceBlock name="breadcrumbs" remove="true"/>` block is used by default, which can be disabled. Try to make sure that it is enabled in the layout file. It is also important to check if you are using a custom theme that may have changed this functionality. If you do not want to manually edit the templates, you can use extensions from Amasty, which allow you to configure
magento breadcrumbs without editing the code, ensuring that the navigation is displayed correctly.