Hi Josh,
Is this a brand new install? It looks like something failed to register during the Python package installation process, or during the scanning of repository types (which would also affect authentication backends and other things). This can happen if you have a Python package dependency error (sadly, we have no way around being impacted by this — it's core Python functionality). If you check the reviewboard.log (enable this if it's not yet enabled) and the Apache error_log, and you see any "VersionConflict" lines, that's what's going on.
The solution would be to address the conflict. If you find those line and show me, I can give you guidance on that.
Christian