Discount not offered

Alynavl89

My car was parked on Elliot Street Car Park, Glasgow (for 2 weeks and a half from 28.03.22 to 12.04.22) and ticket was purchased with the wrong Vehicle registration number for all the period. I received 6 PCN from Smart Parking ( my home address is in England). I appealed the first 5 pcn ( from28.03.22 to 01.04.22), I uploaded the receipts and I was offered to pay the discount £20 . I paid all the 5 PCN. I contacted them on email and uploaded again all the receipts and told them to update the registration number to stop issuing pcn. The PCN number 6 that I appealed was dated 09.05.2022 for parking on 08.04.2022. I wasn't offered the discount £20 so I appealed to POPLA and I uploaded receipts and the appeal response letter but Smart parking uploaded on their evidence a letter dated after I started the appeal at POPLA where they say that an admin error occured and that is the reason I wasn't offered the discount and they offer me to pay £20 for 14 days. But they did not sent that letter . I have not received it. Then POPLA denied my appeal saying that they offered me the discount with the second letter. Now the PCN is £100. What can I do now? Thank you