yes. When the API is protected either by APIKey/OAuth/JWT then you will have “Get access token” link in the details page. If the API is not a protected API, then you dont require a application to access it.
Regarding the issue in generation of application you can check below article.
Debuging application requests raised from API Portal - Knowledge base - webMethods - Software AG Tech Community & Forums
Please check the portal destination in API Gateway and update the user name/passwords configured there (if changed)