It's likely you could be trying to exceed the maximum parking restrictions for the meter or lot that you are parked at.
PayByPhone customers are subjected to the same parking restrictions as customers who pay through a Pay and Display machine. Some areas prevent users from repeat parking after staying for the maximum time allowed by implementing a wait time i.e. 30 minutes.
In this case users are unable to park at the same location, or possibly at other spaces on the same block, until the defined wait time has passed.
For more information on parking restrictions or bylaws, please contact the parking company or enforcement office.