If your park assist is not working, there are a few potential reasons why. First, check to see if the system is turned on. If it is, then the next thing to check is whether or not there are any objects in the way of the sensors. Park assist uses sensors to detect objects around the car, so if there's something blocking the sensors (like a snowbank), then the system won't be able to work properly. Finally, make sure that you're parked in an appropriate spot - park assist won't work if you're trying to parallel park in a tight space or backing into a driveway. If all of these things check out and your park assist still isn't working, then there may be an issue with the system itself and you'll need to take it into a mechanic or dealership for diagnosis and repair.