When I go to mathoverflow.net, I don't see any indication on the page about how to get to MathOverflow Meta. (I think it is supposed to be accessible from the "StackExchange" pulldown on the left of the top bar, but there is nothing there now except a link to the main StackExchange site.)
Possibly related: I don't see any links to chatrooms on the main Mathoverflow page. (I do see such links on the MathOverflow Meta page though.)