Google Ads shows errors for old, deleted pages because Google’s diagnostic tools periodically crawl previously known URLs to verify their status, and these tools may interpret the resulting 404 (Page Not Found) errors or lack of recent tag activity as tagging issues. The system assumes these pages should be active landing pages if they were previously linked to ads or found by the crawler. 

Why this happens

• Googlebot Never Forgets: Google’s crawlers (Googlebot) have a persistent memory of URLs they have encountered in the past. They will continue to re-crawl these addresses occasionally to ensure content changes or deletions are permanent.
• False Positives: The “isn’t tagged properly” message can be a false positive. If a page has been deleted (resulting in a 404 error) or hasn’t received traffic in a while, the tracking tag won’t fire, leading the diagnostic tool to assume the tag is missing or broken.
• Data Retention: It takes time for Google’s various systems to update their data. While a page might be immediately deleted from your server, it can take several weeks or even months for all of Google’s internal systems (Ads, Analytics, Search Console) to reflect that the page is permanently gone.
• Internal or External Links: The old URLs might still be linked from other pages on your website or from external sites. Google follows these links, lands on the deleted page, and registers the error.
• Auto-tagging/Final URL Expansion: Features like Performance Max’s “Final URL expansion” can sometimes automatically generate or test URLs, occasionally pointing to a non-existent or previously active page. 

How to Fix It

You can address these issues with the following steps:

• Implement 301 Redirects: If the content has moved to a new, relevant URL, implement a permanent 301 redirect from the old URL to the new one. This ensures that users and crawlers are seamlessly directed to a valid page.
• Ensure 404 Status for Deleted Pages: For pages that are genuinely gone with no replacement, ensure your server returns a correct 404 Not Found or 410 Gone HTTP status code. This explicitly tells Google that the page should be removed from its index.
• Use Google Search Console: Use the URL Inspection tool in Google Search Console to manually request re-crawling of the deleted pages. This can speed up the process of Google recognizing the 404 status and dropping the URL from its index.
• Ignore in Tag Coverage: Within the Google Ads or Google Tag Manager interface (in the Tag coverage summary), you can often find an option to ignore pages you know are irrelevant or deleted. This will prevent them from appearing in future diagnostic reports.
• Check Campaign Landing Pages: Review your Google Ads campaigns to ensure no ads are actively pointing to the deleted URLs. Update ad destinations to valid landing pages.
• Use Tag Assistant: Use the Tag Assistant browser extension to verify that all your current, active landing pages are correctly tagged and not showing any errors