You're in developer mode, please build and run UI using npm. when building CloudStack from source

[Ronald Feicht]

Hi,

I have followed 
https://docs.cloudstack.apache.org/en/4.18.1.0/developersguide/developer_guide.html 
to build CloudStack 4.19 from source but when I connect to 
http://192.168.17.225:8080/client/ I only get

"You're in developer mode, please build and run UI using npm."

I built the UI using npm, but that did not change anything. What am I 
doing wrong?