Free Parking at GDL

Appears to be free parking at the airport this morning. When I got to the exit, the gate automatically went up without even scanning the ticket. However, when I paid for my parking earlier at a kiosk, the machine was quite happy to take my money!

They scan the license plate at entrance of parking and link it to your parking ticket you get.
At exit they scan your plate again and they know you paid your ticket so no need to give the ticket at exit anymore.