If the upload button is not showing on your product page, you will need to re-install into your theme,
Options
2) Make sure you DO NOT have custom css on your add to cart button
3) Change themes to a default shopify theme to verify everything is working.
4) Edit the Css ID of add to cart button on your preferred theme to match default shopify theme.
* Our app looks for the add to cart button, if you edit the css, and create a unique CSS, our app will not "find" your add to cart and will not know where to put the add to cart button.