The tiptronic functions like a manual shifter. So while the car is running, the lever is shifted to the tiptronic function.
The gear is not supposed to change if you just place the transmission lever to tiptronic. To change gear, trip the lever
once and let it return to the rest position. There is some delay for the transmission in changing gears.
Remember, the gears will not change unless you trip the lever, either + or -.