Each order can have multiple transactions connected to it. These include successful, but also failed transactions.
Transactions are created when the customer chooses a payment method in the checkout. The transaction will initiatially have a state of new, but will soon be set to processing (when the customer is redirected off-site to complete the payment) or completed, when it's done.
If a transaction failed or was cancelled, more information about what happened is available by viewing the transaction information in the merchant dashboard.
- First locate the order on the Orders tab
- Choose View Details in the actions menu
- Scroll to the bottom to the Transactions table
- Click View Transaction Details in the actions menu
The modal window that appears contains all information about the transaction, including a possible error message or user cancellation.
There's a report available, under Reports > Financial in the merchant dashboard, to export a CSV, XML or JSON file containing all transactions during a certain timeframe.