Hi @rockiger @hammaadmemon , I ran into the same problem.
The ReactPress global var is not set in the dev-environment. You should be able to set it in the plugin admin screen on the WordPress install, but that doesn’t work for me. I assume that is because I work on a Windows machine.
The reactpress var is however still set in the production environment on my install, so it runs on WordPress once you build it.
If you have other causes or solutions, I would love to hear it.