Today I got a bug report from a user trying to build an application using gretty 3.0.4, and trying to bump the version to 3.0.5 or 3.0.6 also fails. Browsing the repos at maven central and at https://plugins.gradle.org/m2/ show either versions up to 2.0.0 or nothing at all. This is a recent change, so I'm not sure if it's transient or if it's something you're not yet aware of.