Thanks for the clarification. Something is very wrong there then.
Using TIP mode is a recognised method of checking if the kickdown works as people seldom know in daily life. There is another thread on this, but essentially you drive along in 4th at 30ish, and dump the throttle hard to the floor - thats the only time in TIP you should get a change down, and it won't be a sublte one! (other than if you come to a halt in anything other than 1st!)
VAGCOM it? does that say anything?