I can’t turn on my tracking permission and I am 18 already

Click on this link to learn what it means if an app asks to track your activity --> If an app asks to track your activity - Apple Support

"In some circumstances, the "Allow Apps to Request to Track" setting can't be turned on, including: 

For users with child accounts or under age 18 by birth year, signed in with their Apple ID*"

Make sure you have the correct birthday set. If you recently turned 18, try logging out of your account and back in again as worked for multiple users in this topic --> App Tracking Age Requirements Issue - Apple Community

Click on the link to read how to 'Update the birth date associated with your Apple ID' - Update the birth date associated with your Apple ID - Apple Support

If you wish to ask Apple about this:

Choose your country or region - Official Apple Support

I’m 18 years old I was born October 22 2005