I usually use the Unity Webapps integration with Chromium, but today after an fresh Ubuntu intallation the webapps doesn't work.
What can I do to make an log of it or something like that to find out?
You need the desktop integration package:
sudo apt-get install unity-webapps-service
sudo apt-get install unity-chromium-extension
Reboot or log out and then back in and it should work.
If you allow a webapp for notifications,it will show in dconf: