Replace  WWW::Mechanize::GZip with  WWW::Mechanize and see what happens

Read LWP::Debug and do what it says to your $mech object, and see what output you get (  $mech->->add_handler ...)

Then fireup firefox browser (firefox.exe or ...) install livehttpheaders addon, and compare what the http that livehttpheaders captures to the output that LWP::Debug generates

Then simply tell your program to send same/similar headers as https://metacpan.org/pod/WWW%3A%3AMechanize%3A%3AFAQ#I-thought-Mech-was-supposed-to-work-like-a-web-browser explains