Today: visited T2 to greet friends. Not my first visit and all went well until I went to pay for the parking.
The machine's main screen invites you to insert your Debit/credit card and, lower down, the PIN screen flashes the same message. There is a fixed decal sign pointing to the conventional card slot.
After inserting card - the machine continues telling me to insert card. So I remove and repeate the process. The machine still tells me to insert the card.
Happily, before machine rage erupted, a member of staff arrived and said that the machince
actually wanted me to insert the Debit/Credit card in the
same slot as the original paper ticket.
He was polite and helpful and said that no one understood this.
I mean
What The Blankety-Blank?? 
I was on a different floor to ones I have used before so perhaps that was it? How can they do that - when right alongside is the very smart 'find your cars parking place by your number plate' machine? On leaving the park, the gate did not recognise my number plate (as on all previous occaisions) and I had to fumble for the ticket. Sheesh!