Hi,
First, the post-build step has long since been deprecated. Plus, it doesn’t use the environment variables that are exposed when you turn on ‘Prepare SonarQube Scanner environment’. Instead, you should be using a normal Maven step at the end of your build, as documented.
All that said, this should work anyway if you actually build your project first. But the error message indicates that you don’t:
Please provide compiled classes of your project with sonar.java.binaries property
Ann