3.3.0-SNAPSHOT not available in repository

Hey, i am one of the developers from BetonQuest https://github.com/BetonQuest/BetonQuest and we use the maven-shade-plugin.
Not we want/need to update to java 16.

First i had the following issue: 
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-shade-plugin:3.2.4:shade (default) on project betonquest: Error creating shaded jar: Unsupported class file major version 60 -> [Help 1]

After a small research i found the following: https://www.reddit.com/r/Maven/comments/mw58hq/mavenshadeplugin_java_16/gvgg6hd/

So it seems that 3.3.0-SNAPSHOT (https://repository.apache.org/content/repositories/snapshots/) solved my problem, but i run into the same problem, that the snapshot can not be downloaded.

As a workaround, i tried to run mvn install by my own, and everything works as wanted.

But this is not working on my buildserver (github actions).

Is the artifact broken in the repository or is there something else wrong?