url: AdSense doesn't show ads because Facebook links add a query parameter

Query parameters make different URLs. When Facebook adds parameters, it creates new URLs. AdSense has no way of knowing if the content will be different or not without crawling the URL.

To solve this problem, you can redirect to remove unwanted query parameters. See this question in StackOverflow: .htaccess: remove a query parameter from the URL.

When you redirect visitors to your canonical URL without the query parameter, the ads will be served from that canonical URL and AdSense can display the ads without additional tracking.