https://content.dropboxapi.com/2/files/get_preview issue 409

Hello.

I'm trying to get a preview of files stored in shared Dropbox folder, I'm working on JS and I'm getting this error 409 : path not found.

This is my script::

var dropboxToken = "My_token";
$.ajax({
url: "https://content.dropboxapi.com/2/files/get_preview",
type: 'POST',
cache: false,
//dataType: 'json',
headers: {
'Authorization':'Bearer ' + dropboxToken,
'Content-Type': "application/octet-stream",
'Dropbox-API-Arg': JSON.stringify({
".tag": "path",
"path": "/Pruebas_liveChat/livechat-visual2+(5).pdf//",
}),
//"path": '/Pruebas_liveChat/livechat-visual2+(5).pdf',
},
error : function(err){
console.log(err);
},
success : function(code) {
console.log(code);
},

});