Survey distribution won't send

I successfully sent out a distribution to half my team (3 people) as a test. After hitting send, it took only a minute or two before everything went out.

Then I decided to send a test to 4 more people, but the distribution status has been stuck on "Sending..." for over 15 minutes. Will it ever send?

My account can send unlimited emails, so that isn't a blocker. And I can't find any other reason why it won't complete the sending process.

I need to get this email out to the actual contact list this afternoon (over 1500 people). Is there anything I need to do to get everything back on track?