Some of you experienced this.
You try to put the car into gear or into park, usig the shift ****, but the transmission wont go into the gear you want. Car seems in neutral, and once turned off, it cannot be started because when you try, it complains that you must first place the transmission into park (P).
Well, the most likely fix is replacing the rubber bushing, that is under the car, on side of transmission, on driver side. This bushing has actually been a recall for 955 cayennes, so if you have not done it yet, schedule time to get it done, or sooner/later, you will get stuck.
Over time, this rubber bushing becomes worn, and tears, forcing the shift lever and ball, to separate from the shift cable. Thus, you try to shift gear, but the cable no longer connects to the transmission, creating situation that results in you stuck in a parking lot, wondering what happened.
There are also other possibilities, including magnets under shifter shield (the black felt type material around the gear shifter itself (it has magnets in it, that sense if you move shifter. If they are dirty or fall out, you may also be stuck.

The main symptom that will almost guarantee this is your issue, is that you can move the shifter, but it feels light with no resistance, and does not result in car changing gears at all. After you turn car off, you cannot start it because you see message that says move the shifter to P position.

Well, the small rubber bushing, once bad, will cause the cable to separate. I bought mine on Amazon for 29 bucks, because I needed it next day (prime rocks sometime). eBay has it for 25 bucks, both plus tax, free shipping.
Follow steps in pictures, in sequence. Easy fix. Bushing is stiff, so lube it a bit before you try to force it through the metal loop in the shift cable. It will go, takes time because of limited space in the area. I used a flat tool to bend the side a little to allow bushing to slide through the loop.
Here are the pics. Hope it helps.