It’s OK calm down, don’t panic.
I’m not sure why Yoast has created this slightly frightening message when you install the latest version; Yoast SEO 3.0 but the cynical will think it’s a scare tactic to drum up more business and at the very least get more visits to the Yoast site. I got the same message in the message are and upon clicking the link within I was taken to https://yoa.st this did not help me as there was no information regarding OnPage.org and the what I had to do.
Well I went back to my dashboard and saw the new Yoast widget there. I clicked the “your homepage…” link there and I was taken here: http://kb.yoast.com/article/319-your-site-isnt-indexable
Ah much better. Simple solution: click the “fetch the current status” button and the nasty, scary message should disappear.
However Yoast suggest clicking the green button and see what OnPage.org have to tell you.
Still whatever the reason Yoast chose this way to display this warning it’s certainly going to drive some traffic to OnPage.org and Yoast’s website too.
Update looks cool though! 😀