Hi, the error 10536 in your debugID is returned because your profile, most probably, doesn't allow the duplicate invoice IDs. Several shopping carts use the same invoice ID when a previous payment didn't go through or was abandoned by the buyer. But as the invoice ID was already "used" the system will trigger this error. In this case you can allow the system to use those "duplicate" invoice IDs as follows:
Login to your PayPal account and click on this direct link: Profile Pref
Now select "No, allow multiple payments per invoice ID" under the "Block accidental payments" section and click on "Save"
