How do I turn on tracking?

The tracking function on my iphone is grey-out.

I'm not one of the following:

• For users with child accounts or who are under age 18 by birth year, signed in with their Apple ID*
• If your Apple ID is managed by an educational or business institution
• If your device is managed and uses a configuration profile that limits tracking
• If your Apple ID was created in the last 3 days

How do I turn on the tracking function?