Mixer's legacy self-hosted Maven Repository has unfortunately become non-functional at a short notice and rather than reviving it we've moved our Java Packages to GitHub's Package Registry. You can read about this over on Github's Help Section
If you're not a Java Developer relying on one of our packages, Nothing.
If you're a Java Developer using one of our Packages:
Then you'll need to read the instructions on each package's readme for instructions on how to swap to the new package registry.
If you have any questions please reach out to MixerDevInfo.