Just go to the website every day around noon EST. Click the orange Find a Survey button near the top.

No need to wait for invitations. In the past 3 months, I have received maybe 10 emails. Which I am usually able to click on multiple times.

But I still get a chance to do a survey every day by going to the site. I usually get dq'd from 2 or 3 of them, and then finally get one I can complete for full credit. It is usually a $5+ survey too, plus the 25 cent credits for the ones I was dq'd on.