My credit card is MBNA - but I had to pay separately after it failed in Reservations with Santander too, which was fine. What I don't get is that Cardiff in ACS and Chelsea sale went through ok with my credit card, so a bit puzzled as to what's going on to be honest. Can't phone them, but have emailed asking for a call back - nothing as yet though.
Between the Cardiff & Norwich ACS payments being taken, either the clubs card merchant who collect the money afterwards for them or specific card providers HSBC, MBNA etc have changed the fields required when collecting funds due to the new regulations. So the payments are failing because the ticket office either don't have all the information required or do but are not inputting this.
I suspect ACS payments should be exempt from the new regulations, because they are merchant initiated transactions that have been pre agreed and authenticated when you sign up for the ACS and you as card holder will not be present when the payment is taken. So should go straight through similar to using contactless because it's considered a low risk transaction. That said, I suspect next season the TO will ask supporters to add them to their list of trusted beneficiaries on online banking when signing up to the ACS.
The payment for the League Cup Final was taken at the point of sale as you go onto the website at the time, so could be subject to 2 way verification. Like when you use chip & pin in a shop. When I buy away tickets using Monzo, I always have to go onto the App to confirm the payment before checking out, hence why I didn't use it for the ACS in case the ticket office try & put something through when I've not got my phone to hand. When Leicester & Chelsea away tickets went on sale at the same time I had to verify the 2nd payment because the 1st payment was for the same amount. Which is considered a red flag for card fraud.