Why is my RebelNews+ payment being rejected?

Make sure you are using a supported card: Visa, Master Card, or American Express. The following cards are not supported: Discover, Diners Club, JSB, and UnionPay.
Make sure you are entering the card info correctly and manually. Don't use copy/paste.
Contact your bank. Make sure there are no issues with the card or bank account, that you have enough funds, that online payments are enabled, and that your bank is not blocking the payment.
Clear your browser's cache and cookies. 
(Instructions: https://page.inplayer.com/cacheandcookies/)
Access the website via private/incognito mode. 
(Instructions: https://page.inplayer.com/incognito/)
Try using a different browser (Chrome, Mozilla, Safari, Edge etc.).
Try using a different device.
Try using a different card.
Try using a different payment method (PayPal, Direct Debit, etc), if one has been made available on the final payment screen.