307 Automatic Gear Does Not Change from D to M

Hello,

My 2004 model 307 xt 1.6 triptronic gear stays in D when I shift from D to M in my gearbox. In other words, it still writes D on the display screen and doesn't do + and -. The fact that the vehicle is moving or stopping does not change the problem. I took it to one of the master. They went and connected it to a computer somewhere. They said switch failure. What do you think is the problem?

Thanks..