IT vacancy at the Co-op Bank!
Their reply: .'Thanks for your message. I am sorry to hear this. Our IT team are aware of an issue with security codes.The system will default to putting a '0' into any box that does not contain a number but this will not use the '0' in its place it will show as incorrect.If your code has a 0 in it please make sure to select another number first and then re select the number 0 and this will allow the system to recognise that you have entered the correct information.
Could you also try another browser to rule out this causing an issue as we are aware of a reported problem that Firefox is causing a mismatch for example.'