I am new owner of a Prius v (lowercase v for the Prius v wagon). I've tried the Park Assist a few times just to see how it works, but when I get the rear view mode, I can move the target area, and switch sides, but the "OK" button is grayed out and never comes on. Anyone know what's going on?
Is the target area displayed in red? Does it display a message at the bottom of the screen, especially after you try to press OK? My best guess is that it just doesn't think you can park there - like it thinks you might hit another car, or the curb, or it's too close or too far away. The system is not nearly as good as most humans at parallel parking, so you might not be giving it as much space as it needs; for example, I was taught to parallel park by pulling up exactly even with the car in front of the open space; the car wants you to be further forward, roughly with your driver's seat even with the next car's front bumper. Likewise, it needs a fairly long space - maybe a car and a half in length or so. Anybody who parks in a dense city can get in and out with only an extra foot or so of space. It might help you to try the "pre-assist" function of the parking, which uses the sonar sensors to find an acceptable spot and guide you into it. Press the button by your right knee once, then drive forward slowly (<9 mph) about 3 feet away from parked cars until it chimes twice. Then stop, shift to reverse, hit OK on the screen, and modulate the brake as it guides you into the space. The "pre-assist" function requires there to be a car both before and after the open space, however. (The "pre-assist" for perpendicular back-in parking only requires a car on the near side of the parking space.) Once you've gotten it to work with that mode, you might have a better idea of where you need to start from when not using the "pre-assist".
If the parking box is red, you will not see the "OK" button. Adjust the box until it is green, then the "OK" button will be illuminated. macman408's description is pretty good so I won't repeat it. Alternatively, read through the IPA section of your owner's manual (It might be in the Navigation manual. It's Chapter 7 in my 2010 Prius' navigation manual. It might be a different chapter in yours).
I'm not sure if Enzo has park assist but the ability to parell park is a man-skill and should be mastered without 'assist'