Parking your motorcycle – what’s legal and what’s not? Or what’s going on?

My daughter has parked her motorcycle on the road (to me) because the walkway is very narrow. On the motorcycle there was a note from the city that the holder will receive a notification. The accusation: “You have violated traffic regulations (StVO or StVZO) with your vehicle.” The cars parked there have no notes behind the windscreen wiper and the motorcycle is in standard condition with valid HU apart from the top case. o in Germany Municipalities that demand that motorcycles are not parked on the road? It is known that parking in different municipalities is handled differently, but for two-wheelers suddenly a parking ban applies, if the sidewalk does not allow to park there? Greeting Michael (who is at the moment totally irritated)