I was locking down my Maven Changes Plugin version with the following config:
And then I created the site and noticed the report was empty. The report markup was there, of course, but it generated like my changes.xml was blank. I could run changes:changes-report just fine. However, when I then removed the <version> tag and tried site:site again, the report output was present as expected.
Here's an interesting line from the debug output when <version> is specified:
[DEBUG] The following artifacts were filtered out for plugin: org.apache.maven.plugins:maven-changes-plugin:2.1 because they're already in the core of Maven:
My theory is that because my plugin version has an exact match on the version, my specified plugin configuration is tossed. That certainly seems like a bug to me.