Credit card payments constantly getting denied

[ScreamTruck]

Hello, I have seen this subject in other threads and there seems to be no resolution, but maybe I missed it. Our customer's credit cards are being denied and they are unable to check out. These customers try multiple cards and they're all denied. All of the cards are valid and banks have verified they are in good status. Does anyone have any insight as to why this happens? Currently it's only happening sporadically, but it is very frustrating (and honestly, embarrassing) that this is happening.

[Valentina]

We aren't given an exact reason why a card may be declined, @ScreamTruck - you can learn more about why payments fail by taking a look at this article from our Support Center. I recommend peeking at the Confirm Personal Information and Settings section of the page specifically.

Are you manually entering in these payments, or are you swiping/inserting the cards?