Ok, I have to ask the obvious, do you have an Internet connection?
And if yes, where are you running this from Home or maybe at work?
To do what was done in that other thread youd need to run something like this curl -sS https://raw.githubusercontent.com/pimoroni/get/master/installers/picade-x-hat | bash
Just a guess on my part so don’t be surprised if it also fails.
That was just a guess on my part. It sounds like your router or a firewall may be blocking access to the web site URL? Thats why I asked if you were trying to do this from a work location?
Or you made a typo and or didn’t clip and past the command in properly?