SOAP Call XML Response 417 Expectation Failed

Dear Forum,

I receive an error when requesting an XML as dataset via SOAPCall (endpoint hosted locally) under Windows 10.

Same call executed with SOAP-UI or Python (requests/XMLResponse) on the same Windows 10 maschine responding no issues...

Error-Message:

DataSource.Error: Web.Contents failed to get contents from 'http://endpoint-URL/' (417): Expectation Failed
Details:
    DataSourceKind=Web
    DataSourcePath=http://endpoint-URL/
    Url=http://endpoint-URL/

Query:

let
    Source = Xml.Tables(Web.Contents("http://endpoint-URL:80",[Content=File.Contents("c:\env\Envelope.xml"),Headers=[#"Accept-Encoding"="gzip,deflate", #"Content-Type"="text/xml;charset=UTF-8"]])),
    #"Expanded Table" = Table.ExpandTableColumn(Source, "Table", {"Name", "Table"}, {"Table.Name", "Table.Table"}),

.......

The same query works when PBI-Desktop is running under Windows 7.

Any idea?