In Power Bi when you create a new data source from Web it is possible to select the Advanced option.
In the Advanced option it is possible to add HTTP request header parameters. This is very good, except that many of them are not correct.
E.g. AcceptLanguage is not a correct HTTP request header. The correct syntax is Accept-Language. When usingthe AcceptLanguage header it is sent to the web server, but it ignores it since it doesn't recognize it.
Please review all the header parameter options and make sure they are according to the standards!