Every transaction that happens through PeopleVine (product sales, service transactions, recurring billing, donations, etc..) are all kept track of in the Transaction dashboard [ Sell > View Transactions ].
To view declined transactions use the search filtering and change Transaction Status to "Declined". The search query will return all declined transactions and you can click on the Transaction ID (next to the customer name) to view the complete details of the declined transaction. The reasoning/response is returned from your payment processor / merchant.
You may also have strict settings in place which we recommend you consider disabling to avoid transactions being declined.
Login to your payment processor and look for AVS and CVV settings. Make sure you review those settings to ensure they are not blocking correct payments.
If you are billing subscriptions each month, you will need to remove your CVV settings that decline transactions without a CVV as the CVV is not supplied on recurring billing.