+1
Let me add that you should present clear options and instructions for each:
"Unfortunately, we were unable to settle your invoice via [said cash app]. We're sorry about that, we definitely want to make it easy for our clients to settle invoices. Instead of using [cash app], we ask that you please:
1) (mail a check to this name and address)
2) (call the office with a card number at 555-555-5555)
3) (request a PalPal invoice)
4) Etc
Thank you - we very much appreciate your business!"