In the talk, I mentioned that I would find out why the demos didn't work on the day and explain it all to you, so here it is:
After a few minutes looking back over it in the calm of my hotel room, I found that Payara was working perfectly - the fault was entirely my own!
In the first demo, I start up a few Payara Micro instances without deploying anything. In the second, I deploy the rest-jcache.war file and attempt to curl to it. What I forgot to do was stop the first Payara Micro instances which had no deployments!
So I was trying to access a resource on an instance which had no deployments... D'oh
The second issue I had was with Vagrant. Here, the problem was simply that I was running my 'vagrant up' command one directory too high. Vagrant requires the presence of a Vagrantfile and, under the spotlight, I didn't notice the obvious!