When a credit card or ACH transaction is rejected, the reason given almost always comes from the account holder’s bank and we are simply passing it along. 

For auto pay, you can see general failure messages under Billing Admin > Invoices & Payments on the Billing Overview tab (you may need to scroll to the right in the table). You can see the specific reasons in Billing Admin > Invoices & Payments > ACH Status tab and Billing Admin > Reports and clicking the latest "CreditCard_Processed_Summary" link on the right. Sometimes the reason is self-explanatory, such as insufficient funds or an expired card. But in the case of the mysterious “auth declined” or “issuer declined,” below are several possible reasons.

  • Credit limit, debit card daily spending limit, or transaction amount limit was breached
  • The card has expired (use the Expiring Credit Cards button located under Billing Admin > Invoices & Payments to confirm)
  • The card holder put a hold on the card
  • New card that has not been activated
  • The card was lost or stolen

The card holder will need to check with their bank to get the specific reason. In the case of Lessons or Registration, simply trying the card again will sometimes work. But if not, they will need to use a different card. For monthly auto pay, the family will need to update their card based on the failure reason. They may also need to update their card or payment method found under My Account > My Account > Payment Setup.
 
Once they've done that, you can either use the "New Charge" button in Invoices & Payments, have the family go to My Account > My Invoice/Payment > Make Payment (you must turn on this feature), or ask the family to write a check for this month.

See Also
Can I make a one time credit card charge or refund?
How to manually process a credit card for a registration
If an account is NOT active and they have a CC or ACH against their account will they get charged?