Sample files do not compile with local PlantUML server

[benze]

Hi,

I'm trying to get some some of your samples working locally with the PlantUML 1.2021.01 jar but they are not rendering.

For example, trying to render the acme_c2_workstation.puml file:

$ java -jar plantuml.jar acme_c2_workstation.puml
Error line 170 in file: test.puml
Some diagram description contains errors

Trying to render it in IntelliJ or VSC has the same issue. When I try to render it on plantuml.com server, it renders correctly.

Is there a special configuration I am missing? Or some dependencies that I need to use locally? Downloading the C4 folder and referencing it locally work, although from the samples, I expected that the C4 lib was built-in to the plantuml.jar.