I scrolled down and still couldn't see the checkboxes under the last row. Maybe it also doesn't work on Firefox, because as trivial as it is to make a site that works everywhere no one does. Normally this frustrates me, but if that's the case here it kind of makes sense.
I did exactly that as well. I’m also happy that there appear to be several different captchas, as others mentioned ones I didn’t see. The best one I clicked through was “select every picture with glasses” and every picture had either eyeglasses, drinking glasses or panes of glass.
Mine was "select all checks" and had plaid cloth, chess kings in trouble, checkmarks, x marks, bank checks, etc...
The one that almost got me was the popup with the timer that said "hurry up" but instead of a "go away" box it had a "full screen" box. I don't know how you are supposed to get rid of that box, I had to inspect element->delete node to get past it.
I did manage to finish in a little over 5 minutes.
If you manage to actually 'sign up' it tells you are a legend and rewards you with a Dancing Carlton gif[0].
[0] - https://knowyourmeme.com/memes/carlton-banks-dance/