Uploading files via Google sheets script

Uploading files via Google sheets script

Hi,

I am getting error when trying to upload file to Leads via google sheets script:

Script:

function upload_lead_file() 
{
var result=UrlFetchApp.fetch(attachFile);
var output = JSON.parse(result.getContentText());
Logger.log(output);
}

The error is:
{response={error={code=4424, message=Unable to process your request. Please verify whether you have provided proper file.}, uri=/crm/private/json/Leads/uploadFile}}

Any help appreciated!
Thanks