Use Dropbox API to upload file

Hi everyone, i want to allow users upload file to my Dropbox account and save the file url to Wix Collection DB. Because Wix don’t support many file types and “Get files to Dropbox” app can’t get file url after upload, so i just use Dropbox API only. I followed Dropbox manual here: https://www.dropbox.com/developers/documentation/http/documentation#files-upload
But when i use wix-fetch, there’s something wrong, but i don’t know why:

  1. Here is my backend code:


I used https://kigiri.github.io/fetch/ to convert from cURL to fectch.

  1. For test, i called backend function from click event directly. Json is null after fetch:

  1. Dropbox folder is still empty:


Maybe fetch converting from cURL is not right.
Can anyone help me? My business is stuck here :frowning: