My actual goal is to reply on Messages to particular Items. for that first I am trying to add question from product detail page by clicking on the 'Ask a question' at very bottom of the page. when I click that link it opens screen for selecting a topic. when I select Other , it shows button for 'Contact to seller'. clicking on that button will redirect to sandbox landing page and nothing happens. Can anyone help with this? How can I add message like this so that I can test my reply to message API?