If there was an issue with your Credit Card or Student Loan payment, Digit will notify you that these funds have been returned to your goal. You'll want to fix the credit card account information or the student loan remittance address so Digit can make a payment for you next month.
If you need to make a payment before then, you can transfer the funds to your checking account using the "withdraw" option.
You can view the below steps on how to do that for each goal.
Credit Card
Student Loan