DietPi: MineOS WebUI won’t load locale-en_US.json and is not usable


I installed MineOS using DietPi. I can access the backend but it seems to be broken because some JSON files can’t be loaded. The result is that I can’t install a server. Screenshot:

The error in Chrome is "Failed to load resource: “net::ERR_CONNECTION_REFUSED”

I tried Safari and Firefox. I also tried to run again. Any idea? Here is my log:

Thanks in advance for your help!