Customers' credit/debit cards are being declined

[sibrenz]

Customers' credit/debit cards are being declined. This happened with the last 4-5 customers we have.

PayPal keeps giving "Credit card declined. Please use another card" error message on guest checkouts.

We know there are sufficient funds on their card. We tried processing it on a different payment gateway and it works. 

What could be the reason for this? 

I can't contact PayPal due to their customer service being closed at the moment due to coronavirus.

Hoping someone could help!

[OTIS66]

I`m trying to make a purchase and I`m being declined.