The page that the Play Now button opens tries to open the app via the
wgt: handler. If the handler is working, entering
wgt: in the browser address bar should ask you to open the WGT app.
Even if the handler is set up, it could be disabled in the browser...
In Chrome/Opera the setting is at
In Edge, the setting is at
Firefox allows handlers; see
about:preferences#general > Applications
To test it outside the browser, open the Windows start menu and type "run", click the Run app, type
wgt: then click OK. If it doesn't work, download & reinstall the WGT app (auto-update doesn't set the handler).