We support using cards for purchasing products on this site with the help of PayPal the best payment gateway available worldwide.
But there are chances that purchasing through cards not working or may show some notices about the ineligibility.
Banks usually support internet banking and international banking, but in some of the banks you need to specifically enable these two options from the bank branch or from their online medium. Many of the issues about cards not working is about not enabling these e-banking services.
If you are from a Unsupported country (Where Paypal's direct Card payment is not supported till now) such as INDIA, You may face this issue and you have only one option left that is PayPal native payment method (Where you need a PayPal account) to purchase a product.
Be patient if you can until we come with more payment gateways or your country is being supported.