Can't find root element Lite.pm

Hello,

I am trying to make a connection betweek the OCS SOAP WebService and a C# class.

My OCS server can handle SOAP request, as I can get computers data from perl (https://github.com/OCSInventory-NG/OCSInventory-Server/blob/master/binutils/soap-client.pl) and php (code here: https://stackoverflow.com/questions/36751458/enabling-ocs-inventory-webservice-interface-for-querying-assets-data).

But when I try to make it with C#, using the same XML structure, I get an error: Can't find root element in the message at /usr/local/perl5/SOAP/Lite.pm line 2857, which is: 

die "Can't find ..." unless $request->match($som->enveloppe);

My XML:

 <?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Enveloppe xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://172.23.0.189:80/Apache/Ocsinventory/Interface"
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" 
SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
      <SOAP-ENV:Body>
            <ns1:get_computers_V1>
                  <param0 xsi:type="xsd:string">
                        <REQUEST>
                        <ENGINE>FIRST</ENGINE>
                        <ASKING_FOR>META</ASKING_FOR>
                        <CHECKSUM >131071</CHECKSUM>
                        <OFFSET>0</OFFSET>
                        <WANTED>131071</WANTED>
                        </REQUEST>
                  </param0>
            </ns1:get_computers_V1>
      </SOAP-ENV:Body>
</SOAP-ENV:Enveloppe>

I also tried an other XML, which gives me "Denied access to method (get_computers_V1) in class (main) at /usr/local/share/perl5/SOAP/Lite.pm line 2827":

<?xml version='1.0' encoding='UTF-8'?>
<soap:Envelope 
    xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' 
    xmlns:soapenc='http://schemas.xmlsoap.org/soap/encoding/' 
    xmlns:xsd='http://www.w3.org/2001/XMLSchema'
    soap:encodingStyle='http://schemas.xmlsoap.org/soap/encoding/' 
    xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'>
    <soap:Body>
        <get_computers_V1>
            <REQUEST>
                <ENGINE>FIRST</ENGINE>
                <ASKING_FOR>META</ASKING_FOR>
                <CHECKSUM>131071</CHECKSUM>
                <OFFSET>0</OFFSET>
                <WANTED>131071</WANTED>
            </REQUEST>
        </get_computers_V1>
    </soap:Body>
</soap:Envelope>

P.S: Pour construire ma requête en C#, j'ai repris le format de trame HTTP généré par le script PHP, qui est fonctionnel. J'ai aussi repris les headers pour être sur de n'avoir rien manqué.