Uncompressing xml feed

My application downloads a zipped xml file from the web and tries to create XML reader:

var fullReportUrl = "http://..."; // valid url here
//client below is an instance of HttpClient
var fullReportResponse = client.GetAsync(fullReportUrl).Result;

var zippedXmlStream = fullReportResponse.Content.ReadAsStreamAsync().Result;

XmlReader xmlReader = null;
using(var gZipStream = new GZipStream(zippedXmlStream, CompressionMode.Decompress)) 
{
    try 
    {
        xmlReader = XmlReader.Create(gZipStream, settings);
    } 
    catch (Exception xmlEx) 
    {

    }
}

When I try to create XML reader I get an error:

"The magic number in GZip header is not correct. Make sure you are passing in a GZip stream.

When I use the URL in the browser I succesfully download a zip file with a well formatted XML in it. My OS is able to unzip it without any issues. I examined the first two characters of the downloaded file and they appear to be 'PK' which is consistent with a ZIP format.

I might be missing a step in stream transformations. What am I doing wrong?

You don't need to use GzipStream for decompressing any http response with HttpClient. You can use HttpClientHandler AutomaticDecompression to make HttpClient decompress the request automatically for you.

HttpClientHandler handler = new HttpClientHandler()
{
    // both gzip and deflate
    AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate
};

using (var client = new HttpClient(handler))
{
    var fullReportResponse = client.GetAsync(fullReportUrl).Result;
}

Edit 1:

Web Servers won't gzip output all the requests. First they check accept-encoding header, if the header is set and it is something like Accept-Encoding: deflate, gzip;q=1.0, *;q=0.5 the web server understands the client could support gzip or deflate so Web Server might ( depends on the app logic or server configuration ) compress the output into gzip or deflate. In your scenario I don't think you have set accept-encoding header so the web response will return uncompressed. Although I recommend you to try the code above.