Generic Decline Errors

Some customers are complaining they can’t pay, while others have no problems. I go into Stripe and see they did get the info and see the generic decline error. For what reason are customers getting this? It’s a non-descriptive error that I can’t seem to help customers with, and Stripe’s info on the error is of no help.

{
  "error": {
    "code": "card_declined",
    "decline_code": "generic_decline",
    "doc_url": "https://stripe.com/docs/error-codes/card-declined",
    "message": "Your card was declined.",
    "param": "",
    "type": "invalid_request_error"
  }
}

generic_decline The card has been declined for an unknown reason. The customer needs to contact their card issuer for more information.