So, the receipt shows that you paid for two hours of parking, over an hour after arriving. However, your vehicle is shown being on site for over 3 hours. The PCN was issued for "No valid pay & display was purchased".
The vehicle entered the car park at 11:26. The Pay and Display permit was purchased at 12:31, one hour and five minutes after entry and was valid for 2 hours until 14:31. The vehicle was recorded leaving the car park at 14:38, three hours and twelve minutes after entry.
I'm struggling to see how you can defend this. The driver obviously was aware that a Pay & Display permit was a requirement of the terms and conditions of parking. The driver purchased a permit for two hours of parking but remained at the car park for three hours and twelve minutes.
You did not tell us about this discrepancy. Simply claiming that the driver purchased a "ticket" does not explain why they didn't simply purchase extra time, knowing that they had exceeded the purchased time, irrespective of whether the pay & display permit was supposed to be purchased on arrival or could be purchased at any time before exit.
Regarding the PoC of the claim and whether it was addressed correctly, you must contact the Civil National Business Centre (CNBC) where the claim was issued and the default CCJ obtained. Their number is 0300 123 1056 and you will need the claim number for reference, which you can get from the correspondence about the CCJ