title: What is advanced user for Amazon Product Advertising API?
body: <p>When I register Amazon Product Advertising API, the 'join' button is disabled. Is it because I am not an advanced user? 
  <a href="https://i.stack.imgur.com/Akit6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Akit6.png" alt="enter image description here"></a></p>