I've never used Unity IAP, but as the log states, a consumable item "has already been purchased". The log tells you
onIabPurchaseFinished: false. This means that the in app puchase didn't finish(because apparently you already purchased it). It also tell you
Unable to buy item (response: 7:Item Already Owned), so the cause is: you already own the item.
To fix the problem, you need to call
FinishTransaction to consume the consumable. That way Google knows the user did get his reward, and can complete the transaction successfully.