Issue 

After enabling auditing in self managed environments following documentation https://docs.redpanda.com/current/manage/audit-logging/

auditing was not working and the following error is observed in the Redpanda logs 

Failed to append authentication event to audit log

Detail 

For Audit logging,  SASL/SCRAM must be enabled on Redpanda 

The documentation will be updated to reflect this prerequisite

Resolution 

Use Audit-logging in an environment where SASL/SCRAM is  enabled per  https://docs.redpanda.com/current/manage/security/authentication/