Yes, they’re actually separate.
Adding a Shop tab to your Facebook Page just lets people browse and buy products directly on your page—kind of like a storefront. But when you're running dynamic product ads, Facebook uses something else entirely: a catalog connected to your ad account via Commerce Manager.
So, even if you've added products to your Shop tab, that doesn’t automatically connect them to your dynamic ads. You’ll still need to make sure your ad catalog (the one linked in Ads Manager) is correctly set up, with a product feed, and that it’s the same catalog selected when creating your dynamic ad campaigns.
If the products in your Shop tab aren’t showing up in ads, check:
Is the correct catalog selected in your ad setup?
Is that catalog connected to your pixel or Conversions API?
Are the product IDs matching what’s on your site or pixel events?
Once those are all aligned, your dynamic ads should be able to recognize and use the right products.