By default, the Brands block and the Brands page only show brands that have products with a quantity greater than zero. If you want brands with products that are out of stock to be displayed as well, enable the option Show all for the setting How to show out of stock products in the Customer Zone settings section (Store setup > Cart & Checkout).
X-Cart 5.5.x
X-Cart 5.4.x
Note that enabling the option Show all for the setting How to show out-of-stock products in the Customer Zone settings will not only affect the display of brands but will enable the display of out-of-stock products throughout the store.
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