Hello honda_4,
This page helps to go over the reasons that you may not be able to enable the "Allow Apps to Request to Track" option: If an app asks to track your activity - Apple Support
The page helps to note the following reasons that it may not be able to be enabled:
• For users with child accounts or 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
You can check for profiles that are installed at Settings > General > Profiles & Device Management. Regarding the age, you can use the link here to update the Apple ID's date of birth here, if it shows as being inaccurate there: Update the birth date associated with your Apple ID - Apple Support
Cheers.