Hi Guys
Just circling back to this as this looks like it was quite a random issue which might be useful at a later stage:
please make sure your PC's Cookies are enabled in Internet Properties:
You can gain access to that menu by opening Control Panel → Network and Internet → Internet Options → Privacy → Advanced
Restart your PC after changing all the settings to Always allow/Accept as indicated, then try installing GS-911 Diagnostics again.
Kind regards
Ruan