Currently only statement recipients that are marked as statement recipients when the credit is generated can see Financial aid in their billing details. If a statement recipient is added after the credit has been generated, they will not be able to see the Financial aid. There is no solution if the credit has already been posted. There's a setting when statement recipients are added "Do you want to add this payer as a responsible payer for all existing qualifying charges on this student's account" that only applies to charges. It would make more sense to have this setting apply to both charges and credits.