To start with, change the 'G20' of this post title to 'G 29', so people can identify the wheel
properly.
Have you tried the preset for the G 29? It should work, many G29 owners use it fine with no
problems. Try the G 920 preset just in case this one works, or even an older wheel preset
like the G 27.
Did you calibrate the wheel first in Windows? And, is the power supply connected? If you
have done done the latter, and it doesn't work, you could have a faulty wheel.