引用
This is often a false positive. Imagine you have a connection issue lasting only 5 seconds when Maven 3 tries to download a dependency, it will mark this dependency as unavailable for a delay. And thus will prevent you from replaying the build command even if the network issue is fixed.
Just run the command with the -U option. Even if its description applies to snapshots, it seems to also fix the error if it occurred on a release.
Example: mvn -U clean package