I didn't have to sign up/sign in to take it, so let's see if we can figure out what's going on.
I used Google Chrome to take the survey, and the url above takes me to a main page that looks like this.
Is this different from what you're seeing? It's possible that the browser you're using is affecting the way the site looks.
Here's another link you can try: it's the page that pops up when you click on "Find out - take the survey"
button on that main page.
Let me know if that works out. And if anyone else has any suggestions, please feel free to jump in with your web skillz!