We have now completed our full RCA. Please see the following link for the full details: https://cdn.auth0.com/blog/20200907-Incident-RCA.pdf
Our Engineers have identified that today, between 12:35 and 12:40 UTC, our Preview environment for the EU region was unavailable. During this timeframe, authentication operations might have been affected. Our Engineers identified the issue and applied a fix, which restored the service. We will be releasing a postmortem document within 14 calendar days.
The issue has been identified and a fix is being implemented.