This thread appears to have the info you need to check the magnets and plastic linkage:

https://www.audiforums.com/forum/sho...xing+tiptronic

Check out the link provided by vrso2 for step by step instructions.

http://forums.audiworld.com/a6/msgs/705947.phtml

And hopefully you will find the problem.

It could be limp mode I guess...but then you should notice a definite power loss.

 

If the car isn't shifting at all, it's in limp mode. Usually a MIL will come on, but it should still be scanned for codes. If it's still driving fine, it's likely to be the shifter control.