Recommended Content not displaying in web pages or landing pages when using “category” as a configuration parameter in your recommendation template code to recommend only specific content for the output in the Rich Media template.
You would need to ensure that the content for those specific categories have been enabled for 'Web Rich Media'.
Here is an article on how to enable the content for Web Rich Media. https://docs.marketo.com/display/public/DOCS/Enable+Predictive+Content+for+Web+Rich+Media
Who This Solution Applies To
Content AI / Predictive Content users who customised their content AI code