Also make sure the User Event script has an execution context allowed for "Workflow" in its Deployment(s).
Another thing to check on is that the workflow's configuration of event or scheduled has to do with how it gets initiated, but between States and even Actions within its current State, on a workflow that's already in progress ("Active"), it may or may not be waiting for a user event to trigger it, and if the action that's supposed to trigger your User Event script is in THAT situation, then I think it wouldn't trigger another User Event (NetSuite's built-in way to prevent infinite user event trigger looping).