The easiest and first thing to check is the fuse (there's a list on the fuse panel cover), taking note that the parking lights on the right and left sides are on separate circuits (reasons below), with separate fuses. Thus, it's quite reasonable (if a fuse blows) for the lights on one side not to work, while they work on the other side. And of course, they're independent of the brake and turn signal lights, as well.\


Reason: folks in the U.S. are often surprised by the fact that a lot of european cars have separate circuits for right side and left side tail and front parking lights.
This is done on some European cars because in many countries in Europe, on narrow city streets it's legal to park on the sidewalk overnight provided that the parking/tail lights on the traffic side of the car are left on. And to save the battery, should the lights have to be left on, european market cars have a light switch (different from US market cars) that allows, when the engine is off, to selectively light up the right-only, or left-only, parking/tail lights; thus only half the car is lit, and this halves the drain on the battery.
I found this out when I owned a gray-market Mercedes-Benz with the aforementioned strange light switch.