The problem, it seems, is that you need to install extra packages.
Execute on Erle-Brain:
sudo apt update
sudo apt install -y git cmake python3 python3-pip python3-yaml
sudo pip3 install autobahn rospkg
Then follow the installation guide in the README of the main repository.
When you install everything, launch it:
roslaunch robot_blockly robot_blockly.launch
Finally, open a web browser from a computer in the same network of Erle-Brain and go to:
(10.0.0.1 is the default IP address of Erle-Brain if you are connected via WiFi hotspot)
Anyway, for more information, I leave our blocky documentation here.