Hi @Stacy23,
Sorry to hear about the declined transaction. Unfortunately, the payment is lost. You are not charged a transaction fee, but you are out of pocket for the cost of goods or services you sold. Taking offline payments has its risks due to this; here is a helpful article on offline payment processing.
If you are in an area that does not have wifi, you could always try to hotspot your phone or use a mobile hotspot for your POS.
