Maybe it's your profile picture
Not getting any more greeter games...?

I think they've changed the way that they invite newcomers to greeter games, so there are a lot less being created. The unavailable is just a title, the box underneath just needs to be unticked, like yours is.

See http://www.chess.com/forum/view/help-support/chesscom-computer-wont-let-me-be-a-greeter
Posted by kohai
"Prior to the redesign, when someone joined the site they'd see in their online chess page 'click here to play' then they'd be paired up with their greeter.
Post redesign that message is now shown as part of their welcome message in their homepage inbox. If they don't activate it from there, they won't be assigned to a greeter, hence less greeter games are being created."
I have the box checked that says I will play unrated games as a greeter and I have the maximum set to 50 games. I have played 21 so far and I'm not getting anymore. I also see a little stop sign which says Unavailable - and I'm not sure what that means...see below. Anyone know what's up with that? Maybe there just aren't any new members that want to play greeter games?