Could you share the configuration details of your Anaplan connector object? The connector can't locate an import action that matches the name/ID provided, does the value in Mulesoft match exactly what appears in Anaplan?
Jesse Wilson Solution Architect - Data Integrations Singapore
It's not required to use the ID when referring to the workspace, model, or actions with the Mulesoft connector, you can refer to them by name. If you do want to use ID, you can obtain them with API calls. Using a utility such as Postman makes this much easier. Select Basic Authentication, and use your Anaplan credentials. The endpoints will be https://api.anaplan.com/1/3/workspaces/<workspace ID>/models/<model ID>/(imports, exports, files, or processes depending on what information you need)
You just need to define one additional header: Content-Type:application/json