Error creating an XML file

Error creating an XML file

I am creating an xml as string in the function Employee.generatePartA_XML_String, and then I want to save it as a file to the field "Part_A_XML", but I get the response:
{"code":3700,"message":"Unable to upload a file. Please check and try again."}

How can I fix this?

This is the code:

        xml = thisapp.Employee.generatePartA_XML_String(recordID);
xmlFile = xml.toFile("Employee.xml");
xmlFile.setParamName("file");
fileName = "Employee.xml";
xmlFile.setFileName(fileName);
reportName = "Employees_Report";
response = invokeurl
[
url :"https://www.zohoapis.com/creator/v2.1/data/" + zoho.adminuser + "/" + zoho.appname + "/report/" + reportName + "/" + recordID + "/Part_A_XML/upload"
type :POST
files:xmlFile
connection:"zoho_oauth_connection"
];
info response;