My Webapp is showing an empty start page.

Debugging: F12 / console =>
Uncaught ReferenceError: Lianja is not defined

All Lianja.xxx statements are listed with the same error.
(The js script is not mine).

There may be some reference missing in the web app.
What could that be and where do I have to enter it (in the app's properties?).

I could also share a link to the app here. The app works without login...

Thank you for help
Georg