It might happen that the advanced drag&drop asynchronous uploader does not work, failing with a “-200: HTTP Error” or similar.
As of experience, this is likely caused by too strict server security settings. The uploader uses plupload and POSTs the file to the URL
Another source of failure might be other plugins inserting invalid error messages or whitespaces into the JSON data of the server response. So before you further stick into this, just disable any other plugins and try again. Then re-enable them one-by-one to spot the conflict.
Here’s how to get details about the error for debugging, which is essential when you ask us to help you on this:
- Navigate to the file add form with the broken uploader
- On Chrome+Windows Press
Cntrl+Shift+Ito open the Developer Tools. See detailed instructions for other OS. On firefox it should be the same, see Mozilla’s documentation.
- In the Developer Tool box, open/navigate to the Console. The should be a tab with this name, otherwise press
Esc. You can alternatively open the console directly with the hotkey
- Now start uploading a file and look for error messages in the console after the file upload completed.
Post this in the support forums or create a ticket.