Your Product Owner is a fraud and should be immediately replaced if they cannot in very simple terms explain:

1. why the product is being built – what value does it bring to the business in terms of ROI;
2. why the product is being built – what value does it bring to the customers, why should the customers use it;
3. what actions should the customers take to get any value from using the product.

Everything else is pretty much secondary. These three points, however, are non-negotiable.