Problem : The manual authorization on Qnap takes you to Google Authorization page, when you click on accept, it closes the window and takes you back to the Authorization window on Qnap. You never are able to get the authorization code.
Solution : Right click and get the authorization link by right clicking on “Click this link to get the authorization code” in step 1. Paste this code in a different browser window. Now when you click on accept, it will give you a token that you can input in step 2.