AWS CloudFormation Template: CoreOS error once deployed?

So I've just deployed the provided CloudFormation template into my AWS environment. I've actually done it a few times now as it keeps getting the same errors every time. 

Nothing comes up on port 80 from it, and when I SSH into the CoreOS instance, I get:

Container Linux by CoreOS stable (1688.5.3)

Update Strategy: No Reboots

Failed Units: 1

  oem-cloudinit.service

I've never really used CoreOS before, and I can't find where to look for logs even to see why this is going wrong. Any ideas/pointers as to why this is failing for me, and how to rectify this to get it booting up properly?