There’s not enough info for me to see where the problem is. So move your setup to a passing state. Then you can make one change at a time to your ideal state and then you’ll know that is the thing causing the problem. Some ideas below.
Have a look in your local _site directory to see if your product page got created. Then you know it was included. You might have to clean out your home.md to not cause an error so you can get as a passing build.
Your config setup for include looks correct.
Can you try put your page in the root first and see if that works? Then move it to _pages later.
Can you share the name of your username and repo name e.g. abc/def or the repo URL.
The problem might be none of the things above mentioned but specially URL.
What is the point if the url param in your homepage? I can’t see the rest of the frontmatter but setting a single url to point to another page seems weird. Also, page.url is already a property set by Jekyll so you should not override it.
What are you trying to achieve? Add a link to the product page in the body of homepage, or navbar? Can you provide any links to docs for the theme which show how and why the URL field is used?
Can you get a demo of the theme with light content to work? Like in a separate repo.