when I use dropboxAPI to delete file, I get 500 error. why?

Thank you for your reply; when I run my app as user privilege ,All works well. but run as system privilege , I receive statusCode=500,All response message: 

HTTP/1.1 500   

Cache-Control: no-cache

Content-Type: text/plain: charset-utf-8

server: envoy

Content-security-policy: sandbox allow-forms allow-scripts 

x-content-type-option: nosiff

accept-encoding: identity,gzip

x-dropbox-response-origin: far_remote 

use code like: WinHttpConnect(hin,"api.dropboxapi.com",443,0);

                 WinHttpOpenRequest(**,"POST", 2/files/delete_v2.**);

                 WinHttpAddRequestHeader("Authorization: Bearer *******");

                 WinHttpAddRequestHeader("Content-type: application/json");

                WinhttpSendRequest(**, "{\"path\": \"/work/path\"}");