Notices have been placed on the car park's payment machines stating that there is "temporary and intermittent failures with the car park payment system".
The problem means that parking can't be paid for by debit or credit card, as well as £5 notes.
It adds that "engineers are working hard" to fix the issue, as well as the whole car park system being replaced in 2019.
The full notice reads:
"We are experiencing temporary and intermittent failures with the car park payment system.
"Engineers are working hard to restore service as soon as possible.
"In the meantime, we can only accept cash payments as the Credit Card facility is not available.
"With cash payments, unfortunately payment with £5 notes is not available.
"The car park system will be replaced during 2019 to provide shoppers with the very best technology and service standards.
"We apologise for any inconvenience caused to our shoppers while the car park equipment is being restored."