Check LastException. This error means that you have already purchased this item. You should call ConsumeProduct to remove it.
I called ConsumeProduct than I restart the purchase process and the result is the following :
1) In-App purchase UI says purchase OK.
2) The _PurchaseCompleted event report Success = false with the following error in log :
Purchase signature verification FAILED for sku android.test.purchased
Signature verification failed for Product ID android.test.purchased (response: -1003purchase signature verification failed)
After this if I ask a new purchase I got :
"Unable to buy item, Error response: 7:Item Already Owned"
So before I got a "Signature verification failed" in purchase process and than It seem Owned ?
I'm I little confused.