It's probably because of referrers, opened it in an incognito window and it worked just fine.
https://www.newgrounds.com/tubby/netfreedom.html
This is the page I was referring to. Looks like the nonprofit involved might not still be around?
https://www.newgrounds.com/tubby/netfreedom.html
This is the page I was referring to. Looks like the nonprofit involved might not still be around?