It means that you can not withdraw the money from the customers payment card, and then the payment gets suspended. It tries 6 times during the duedate. If the problem persists, and there is not sufficient funds on the customers cards, or if the card is expired or etc, then the payment will fail. Suspended is a status internally for MobilePay to mark hiccupped payments, which is why it is not a part of the callback table on the documentation on GitHub
Note: MobilePay does not tell you the specific reason why there are troubles with the card, as we are not allowed to give that level of detail.
In short, the Merchant should contact the customer, and have it cleared out with the customer.
The user receives a push notification, if there was an error with the card for example, so we always try to catch errors.
If there were insufficient funds on the customers card, we also push the customer to execute the payment manually.