The other possibility is that the entry in SWEL says something like "Exception" or "Check FM ends with exception". These options mean that the event was raised and that the workflow did try to trigger but could not do so for various reasons.
It the event the linkage shows a green LED, it means that the workflow did trigger successfully but may have "hung" in subsequent processing. You can view the workflow log or check the inbox of your Workflow Administrator for more information.
Dig Deeper on SAP workflow development
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