tip: arthur merlin words>1000 sort:hits
Have you posted at least 10 comments? That's one of the criteria for having received an invite. If you have posted at least 10 comments, then you should have received the invite. Are you following the directions listed above to locate the invite?
Of course, I left way much more than 10 rws since I joined. I think I left over 10 rws just in this month... And invites isn't hard to find from the dashboard you see the option right away, but it take me away to that we-are-sorry-this-option-is-closed-now error as before..
Then I have no idea why you don't have an invite :( Maybe email Support and ask? The admin don't check the comments on these posts very often, so you might not get a response here.