can't go into reverse..

[Bavarian Motorist]

I can't go into reverse. The shifter will not go into reverse. It will go into all other gears (1-5). It is cold, so I waited for the engine to heat up to 175. Still nothing.

I called porsche roadside assistance and they are coming to tow it in 70min. If anyone can help me before then I would appreciate it. What could the problem be?

Also, I don't know if this is normal, but when idling, the tachometer needle twitches a little bit, and kind of goes up and down by maybe 50rpms, back and forth. Is this normal..?

I really love my car, even though it's brand new, and I want it to be okay and to be able to trust porsche again for my next car.