This can be caused by the vehicle, programmer, key, or user. If the vehicle has a damaged OBDII port it will not be able to communicate with the programming device or if the vehicle's battery is too low of a voltage.

 If the programmer is damaged or needs an update it may not be able to communicate with the vehicle. If the key is bad and is not getting paired with the vehicle then it can cause a communication error or a “successful program” but with it not working afterwards, or if it is just the incorrect key for the vehicle.

This can also be caused by the users- if they do not have the key in the “ON” position, if they do not have the programming device properly set up, if they do not have the correct MMY, if they have chosen the wrong programming procedure.