Can someone tell me whats wrong with this API call?

I am updating CRM invoice record using the following xml string:

<Invoices><row no="1"><FL val="Id">16611480000139713</FL><FL val="Shipment Date">2017-07-28T15:53:49.0000000</FL><FL val="Tracking Number">94055118984638900252</FL><FL val="Shipment Status">Completed</FL></row></Invoices>

Here is the URL to the API end point

https://crm.zoho.com/crm/private/xml/Invoices/updateRecords?authtoken=xxxxxxxxxxx&scope=crmapi&xmlData=%3CInvoices%3E%3Crow+no%3D%221%22%3E%3CFL+val%3D%22Id%

22%3E1661148000013974413%3C%2FFL%3E%3CFL+val%3D%22Shipment+Date%22%3E2017-07-28T15%3A53%3A49.0000000%3C%2FFL%3E%3CFL+val%3D%22Tracking+Number%22%3E9405511898463890025492%

3C%2FFL%3E%3CFL+val%3D%22Shipment+Status%22%3ECompleted%3C%2FFL%3E%3C%2Frow%3E%3C%2FInvoices%3E

But I am getting the following error message everytime:

<response uri="/crm/private/xml/Invoices/updateRecords"><error><code>4600</code><message>Unable to process your request. Please verify if the name and value is appropriate for the "id" parameter.</message></error> 

Thanks in advance.....