Credit does not stay applied to charges on Activity tab of record. It will not stay applied even after choosing to "Unapply all and Distribute Evenly to Current Payers" for the Credit and the Charges. The charges are in a closed fiscal year.
Change the Project the charge is associated with from Inactive to Active in General Ledger.
1. In Student Billing>open the Charges that the credit will not stay applied to 2. On the GL Distribution tab>note the Project ID 3. In General Ledger, go to Records > Projects 4. Open the appropriate Project 5. On the Project tab, select Active in the Active/Inactive drop down 6. Save and Close 7. In Student Billing, apply the credit to the appropriate charges