This error message indicates that the ATO has already received the event and that it has been lodged multiple times.
This may have occurred because there was an issue processing the response the first time and so an attempt at lodgement was made again.
If you've already lodged the pay events but you want to make a correction to what has been lodged, submit an Update Event instead.
Thanks for following up on this thread.
I would recommend lodging an update event then lodging the finalisation event to make sure we have covered all bases.
For more information on how to lodge an update event, use this article here