Hope you solve the redirect_uri_mismatch problem. If you want to upload your all product at a time then forget about the single product submission and go to the products feed tab.
1. Now fill the form and generate your product feed. You can generate feed for all products or some individual product by product field.
2. Download the feed xml file from products feed list tab.
3. Back to your merchant account and go to feeds menu and upload your downloaded feed xml file and submit it.
4. After submit If you get error then you have to fix it. But don’t worry about the warning.
5. If you do not get any error then wait for google varification.
It also work for product variation and product attribute such as color, size etc.