Possible Reason: Current business date (Picture 1.1) is different from payment date (Picture 1.2).
Image 1.1
Image 1.2
Solution: Do daily close for current business date and login to that payment’s business date (Image 1.3,1.4)
Image 1.3
Image 1.4
Do cancel payment as usual, now system will allow you to cancel the payment because the current business date is same as the payment date.
Image 1.5