New Install Didn't Calculate It's Mesh IP Address

I had a bit of trouble installing AREDN on a new Rocket M5 because the reset button was flaky. There is no tactile feedback, and I was just missing the button with my magic paperclip. Eventually it came up with the 1-3, 2-4 dancing LEDs on 192.168.1.20 and I was able to upload the AREDN image. I did not need to set up a DHCP server.

However, once the node was up and reachable on 192.168.1.1, it came up with the node name "NOCALL", and the mesh RF IP set to 10.0.0.0/255.0.0.0. I couldn't save this configuration, it refused with a "Invalid Mesh IP address" error. I thought the new install was supposed to configure its own Mesh IP? 

I set the hostname to KF6IIU, set the root password and nothing else, rebooted the node, and now it has the host name NOCALL-162-169-109, so it looks OK. What did I do wrong initially? Or is this expected? 

The image I used is aredn-3.22.8.0-ar71xx-generic-ubnt-rocket-m-xw-squashfs-factory.bin.