Through my AGOL account, I created an app in WAB developer. It has two widgets and one feature layer, none of which require a subscription. After creating the app I downloaded the zip from my Content menu in AGOL. I extracted to a folder on our organizations server.
In the Readme:
it says to add the AppID to the config.json, which I did.
I don't understand why it's asking to Add and Register the app when it's already in the Content with the App ID. (or maybe this is what the Note in the Readme is referring to).
The error says it's unable to load the config.json. The only thing I did was add the AppID to the config file.
I asked this same question in Geo Developers as well.