If the database is enabled for another external authentication scheme, verify that you want to use IAM on the Autonomous Database instance. There can only be one external authentication scheme enabled at any given time.

If you want to use IAM and another external authentication scheme is enabled, you can either first disable the other external authentication scheme or use the force parameter with the value set to true when you enable IAM authentication. See Enable Identity and Access Management (IAM) Authentication on Autonomous Database for information on using the force parameter.