It won’t even recognise the card as a Debit Mastercard to continue to payment.
Maybe try clicking credit card if there’s the option.
Also email firstname.lastname@example.org
No option available.
Looks like they use SagePay as a payment processor so they’re the ones not accepting.
Don’t think I’ve had issues with sage pay before…
Don’t shoot the messenger! I’m just saying that’s who they use.
I know. No vitriol intended and definitely not against you. Just a neutral statement of fact to assist with logically working through troubleshooting.
Have never seen this non valid card number error either.