If you do a resend and the workflow starts correctly, maybe your data is not yet saved to the DB at the time the workflow starts and the start condition could not be evaluated. I suggest again that you try re-sending the event via the event browser in SWEQADM (Click on the 'Browser' button and select 'All events' as well as 'Other events' & 'Events not delivered' and you should see the event and be able to resend it)
That way you will know for sure that nothing happened in the system, if the event will be process well by doing this, then the event might be raised before the commit.
You can also try removing the starting condition and checking if the workflow runs well.
To the best of my understanding the check function module is run by the session raising the event. the event processing is run by the workflow logical RFC in a new session an has a greater possibility that all DB updates have finished. If this is the case you can transfer the starting condition check to within the workflow. or since this is a standard workflow - check for notes/report a product error.