If at any point in the delivery process one of the statuses (maybe not the right word) happened in an offline state, the order will require a final 'Completed' action. It is important this 'Completed' button is pressed when the device is on a network.
This will clear the orders from the device. If this action does not clear the orders from the driver's device, please clear the app data.
Should this not clear the orders then please contact Cowabunga Support team