Java does not find the codegen or other jar files:

Newer Java version only accept the class path syntax. This means you have to update your Makefile or built scrips. The class path must be adjusted according your installation of course.

On Linux/Unix/Mac use the following format:
-cp ../../bin/*:../* codegen.Main

On Windows use this format (even displayed differently here use normal quotation marks):
-cp “..\..\bin\*;..\*” codegen.Main

The code generator has problems to find Astah models

The code generator uses the public API to access the Astah models. Therefore the Java class path must contain the path to the Astah Java API. The following class path shows how to do this. Take care to consider class path differences under Windows and Unix like systems.

-cp “..\..\bin\*;..\*;C:\Program Files\astah-professional\*” codegen.Main

Also make sure the file extension is according to the Astah rules. Otherwise Astah does not accept the files as input model:
For Astah Professional: .asta
For Astah SysML: .asml