Form Stopped Sending Main

I’ve been running this form for a week or so now and I’ve already recieved one submission through it (past the initial testing which was fine).

Now all of a sudden it’s stopped sending mail. I noticed because I installed the plugin on another site and couldn’t get it to work. Tested my original site to no avail.

Is anyone else experiencing this issue?

http://www.blackinkmmg.com/index

http://wordpress.org/extend/plugins/si-contact-form/