Magic keyboard finger ID set up

By the looks of things, you said you are running OS X 10.10?! Only Macs with an M1, M1 Pro or M1 Max chip, that run minimum macOS Big Sur, can use the Touch ID sensor on the Magic Keyboard. Reading the compatibility section in the apple shop webpage for the Magic Keyboard with Touch ID confirms this.

Raffael_23 wrote:

I have a MacBook Air and it's about 2 years old, and am running Monterey 12.1.

GreeniusGenius has a point. Your MacBook Air may have Touch ID but you need an M1 MacBook Air to support Touch ID on an external Magic Keyboard.

Okay. So what happens when you select System Preferences > Touch ID to set it up?

Which Mac, model & year do you have? Your signature indicates you are running OS X 10.10 which I assume isn't correct.

Did you read: If Touch ID isn't working on your Mac - Apple Support