Application with parameters fails to connect to data

I have created an App from a published report in an app workspace. The App uses parameters to specify the ingredients used for the connection string of a ADLgen2. 

After the app has been installed and I try to connect to data it shows two of the mandatory parameters - another parameter has been marked as locked in the app wizard. Yet it fails to connect. At this point I would expect a dialog to show that requests the key for the data lake - as it does when using a Power BI template (pbit file) of the report.