Can't enable Personnalized Ads and Apple Advertising

*I found this article *Why is “Allow Apps to Request to Track“ grayed out on my iPhone?Indeed, why is “Allow Apps to Request to Track“ grayed out on your device? People who are faced with the same issue will find the answer in a support document on Apple’s website which lists a few instances when the “Allow Apps to Request to Track“ setting may be grayed out:

• If your Apple ID was created in the last three days.
• If your Apple ID is managed by an educational institution or uses a configuration profile that limits tracking.
• For users with child accounts or under age 18 by birth year, signed in with an Apple ID.

An important thing to note: child account age varies by country and region.

Don’t worry about being tracked while this setting is greeted out—Apple says that in any of the aforementioned cases, all apps that request to track you will be denied permission by default. And should the status of your Apple ID account or device change down the road, you will be allowed to toggle the setting “Allow Apps to Ask to Track” on or off at will.

My Notes: This is what I found about this issue, I am guessing it will be able to toggle the next time Facebook tries to track you. If not try to reinstall Facebook and as a last resort to go Settings > General > Reset > Erase all settings (Not Erase all Content and Settings)

Just go to Settings -> Privacy. Scroll down and tap on ‘Apple Advertising’. Then, just disable the toggle next to Personalised Ads.

This should help!

*I did not write the instructions

Based on what I am seeing you don't have any apps that support personalized adds so you can't enable it. Only a few apps like Facebook do it.

this YouTube video might explain it.