If, for whatever reason, a transaction fails to sync with DonorPerfect you will be notified with a red banner across the top of your Transaction History screen (Contributions > Recurring Transactions).
You can easily re-sync a transaction by:
Clicking the red 'Show Transactions' button
Clicking the magnifying glass icon to the left of the transaction
When the modal appears, select the 'Resync' button
Having trouble re-syncing? Check out this article to help you troubleshoot!