Trouble with XML prestashop API POST


I’m trying to change my Prestashop 1.6 inventory by using RESTfull API but I have to send an XML body with the changes, the trouble is that when I try to send the POST request, it sends me this message:
Raw response for the API
Status code 500

<?xml version="1.0" encoding="UTF-8"?>

I have tried to send the body as a JSON and also as an XML with no success, I would really appreciate any help with this :slight_smile: