Error with push notifications: applicationServerKey is not valid

[julia-r]

Hello,

I am trying to get push notifications running. The service worker seems to register fine, but when I try to subscribe, I get this error message in Chrome (version 89.0.4389.90):
pwa.js:182 PWA: Unable to subscribe to Push DOMException: Failed to execute 'subscribe' on 'PushManager': The provided applicationServerKey is not valid.

Here is my test setup: https://pwa-test.gruenewuerfel.de/

I noticed that in the config.js Line 36 it says 'YOURAPIPUBLICKEY' Do I need to replace that with something? What kind of key do I need?