I’m over 18 and I won’t let me turn on tracking.

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

*I wonder about that "by birth year" bit. If it is going by year alone it may think you are still under 18.

If you wish to ask Apple about this:

Choose your country or region - Official Apple Support

If you cannot sign out it may be that somebody has set restrictions on your account. If an app or feature on your device is not working, not appearing, or is restricted (grayed out), it may have been disabled using Screen Time, or by an IT administrator if you are using a device owned by an employer or educational institution.

- Read this support article If your Apple ID or other options are greyed out in Settings —> If your Apple ID is greyed out in Settings - Apple Support

Tap Settings > Screen Time > Content & Privacy > scroll to Allow Changes and turn on.

- If the device is managed (Settings > General > VPN & Device Management), contact the IT department that is doing the managing.