@jochen I have seem to fix the issue. I found that if I download the source code from the git repo (and change to the tag branch 2.3.1) I have success! But if I download the code from the release page (the zip file) and build I do not get a version number. The reason being is when you run mvn install you get the following error.
[INFO] Storing buildNumber: null at timestamp: 1504106889375 [WARNING] Cannot get the branch information from the git repository: Detecting the current branch failed: fatal: Not a git repository (or any of the parent directories): .git [INFO] Storing buildScmBranch: UNKNOWN_BRANCH
Even though checking the target/classes/version.properities showed 2.3.1 I don’t think the version number was correct accross all compiled code.
TLDR: must build code from a git repository. not the source code zip file.