Receiving a fine is never pleasant. To identify why it was issued, you can do the following checks:
The start and end time of parking.
The zone code of the parking place.
The selection or license plate number.
If everything mentioned above is correct, you probably had a valid parking and therefore you can request the withdrawal of the fine to the parking operator of the city in question. To speed the procedures, remember to send a photograph of the fine and the parking voucher, which you can download both from the app and from the web.