Error configuring Cluster in Management Console

I have verified I can ssh as dbadmin without providing a password.

But when I try to "validate Hosts" in the Manage Console (MC) It show this error:

Validate hosts failed. Reason: SqlMapClient operation; SQL[];--- The error occurred in create-cluster-step-sqlmap.xml.--- The error occurred while applying a parameter map.--- Check the createClusterStep.deleteByHostId-InlineParameterMap.--- Check the statement (update failed).--- Cause: java.sql.SQLTransactionRollbackException: Container was opened in read-only mode.; nested exception is com.ibatis.common.jdbc.exception.NestedSQLException:--- The error occurred in create-cluster-step-sqlmap.xml.--- The error occurred while applying a parameter map.--- Check the createClusterStep.deleteByHostId-InlineParameterMap.--- Check the statement (update failed).--- Cause: java.sql.SQLTransactionRollbackException: Container was opened in read-only mode.

In "Show Detail" it show another error:

Success: Test: Validating Ping: INFO: Ping succeeded.
Error: Test: Validating SSH connection: ERROR: athentication failed for user root. Could be because SELinux is enabled on the host OR a wrong private key is being used. If the problem still persists, please contact your administrator or HP/Vertica support.

My question is: why this second error indicates "failed for user root"? The default user is dbadmin, and I have configure ssh by dbadmin.

I hope you can help me.

Thanks,