Ok, so I enabled the button through the developer tools from the browser and requested a review; No additional form was shown, the assignment status now shows it was submitted. Since it wasn't showing any previously sent messages, I sent another one with the model attached.
The interface is somewhat confusing, the round# tab says sending messages/files does not submit the request and indicates to do so using the submit button below it (The submit button is at the top of the page right below the header, not below the Send Message button).