Azure VMs: Waiting for SSH to be available


I’m attempting to create a Node Pool of CentOS VMs and have not been unsuccessful. After the VMs are spun up, I get the Rancher error message: "Waiting for SSH to be available… " and eventually it times out after 60 tries. I cannot figure out what the problem is nor can I find anything in the variety of Google searches I’ve tried.

Here are the details of the Azure environment
Rancher VM:
RancherOS (rancher/server:preview)
Node Pool:
OS Image: OpenLogic:CentOS:7.3:latest
Username: azureuser
Open Ports: all defaults plus 22/tcp