Is the collection set as available to the online store channel?
Is/are the products within the collection set as available to the online store channel?
I know you said the menu is correctly set, but have you 100% verified that the URL matches the URL listed in the collection setup page?
Do you have any kind of apps installed that are set to hide products for certain reasons (out of stock, based on geo location, etc.)?
I know it may be silly to ask and I'm sure you already have, but after you finished setting up the collection and before you went to view the site did you clear your browser cache (or at least refresh a few times once you were on the active site) to make sure the updates were loaded to your browser?