I'm new to payment integration. I have integrated a payment gateway in our software but when I tried it using my card, it was declined saying that "Unfortunately we could not add this card. Try again later or use a different card." or something like "card has been declined please try a different payment method". Payment through paypal successfully went through but I want also the other payment method to work like pay using Debit/Credit card. I tried to use sandbox credentials and it is also working. Is there something wrong with the code or is it because of my card?
Any response is well appreciated. Thank you!
It means processing that card was declined. Don't use your own card to test PayPal payments, such test payments will often be blocked, especially in the live environment.
For sandbox testing, you can try with a card from https://developer.paypal.com/developer/creditCardGenerator -- although if you are integrating a standard PayPal Checkout it is not necessary to test the black button; for integration purposes you can test everything you need to with as far as payment completion/capture with the yellow PayPal button.