You are correct that this typically means you are missing some authorization for the currently authenticated user. To help you with this issue, I would need to know a lot more about your NiFi-Registry setup configuration.
1. nifi-registry.properties file would tell me which method of user authentication you have setup, any identity.mappings you have setup, and which authorizer you are using. 2. identity.providers.xml file tells me how the login provider if used specified in the above nifi-registry.properties file is configured. 3. authorizers.xml file tells you how the configured authorizer specified in the above nifi-registry.properties file is configured and what user-group-providers are being used. 4. Depending on configurations used in authorizers.xml, you may have a users.xml and authorizations.xml file generated as well or you may be using an external authorizer like Ranger. 5. I would need to know your user string (case sensitive) that is displayed in the upper right corner of the NiFi-Registry UI after you login/authenticate into nifi-registry, so that it can be checked against the configured policies to see what your user is missing.