I need you to tell me the year of the vectra or at least if it is A, B, C, or D.
depending on the year of the car the central console is disassembled in one way or another, the first thing is to look at the fuses of the car's cabin to make sure that there is none burned. With the help of the instruction manual in which the functions and abilities of each fuse come detailed you will have to identify the fuse in the box. If it's okay then it will be to disassemble the central console and look at what happens to the roulette.
Normally, when the roulette is broken only the maximum speed works, but other times it stops working and point.
If you have to disassemble the console tell me and also put the year of the car so that I can guide you ok?
All the best.