RingGo's parking service is designed to be used in the same way as the on-site payment machines, whereby the session begins at the point payment is made.
Unfortunately we are unable to take payment retrospectively when customers forget to pay for their parking or should their mobile signal fail, etc. This is primarily because the operator responsible for enforcement in the area may have already issued a charge notice in the interim.
If people were allowed to pay for their parking after the event, we are sure you can appreciate that some of the dishonest amongst us would risk not paying for their parking initially, and only in the event a charge notice had been issued would call RingGo to pay for their parking to avoid the larger sum of the fine. This would offer customers no incentive to pay on arrival!