@CactusJack As and when user browse, over certain period of time generates the interest categories and the ads are triggered over those categories available in the catalog. Can you please check this
https://ads-serve.brave.com/v1/catalog whether catalog is empty or Ads are available for your region?
If it’s empty, Ads are not available. Ideally for supported regions Ads should be available (US, Canada, UK, French and Germany)