Are you running this from the sandbox?
Are you using the Sample Email or an actual "live test" by sending a batch? It's a little unclear. Usually you can send batch emails from sandbox, but some firms may have asked Marketo to disable that.
Sample Emails are known for disappearing for awhile. If they aren't in your spam box, then it's possible there's an error on the marketo backend. Ask support.
Hi Katie -
Have you run an email report to see how the email send did? That might quickly tell you what happened with it.
I ask, because Sandbox instances are not generally set up with SPF and DKIM, or branded tracking links, and this can sometimes cause emails to get caught in spam filters before you ever receive it. (you can find more information about SPF and DKIM for email deliverability here)