Hi,
The problem is that you set 'Archive' in the 'Processing mode' of your adapter. It processes this mesage again and again (so, notifies you about duplication problem). You need to think on the question - why processed file does not disappear and gets processed again? Mainly, it's due to the fact, PI doesn't have an access to 'Archive' directory you specified in the adapter. Normally, you would need to give an access to 'SAPService<SID>' user to shared directories... or, maybe shared directory is not accessible dur to the network-related issues.
Hope it helps.