Purchase Date not Validated

Because whoever sold it to you did not notify Apple of the sale as of the time you checked. It can take a couple of days to update the warranty database, but if it is past that check here → Check Your Service and Support Coverage - Apple Support

If it doesn’t show your warranty status see this support link → Correct the purchase date or expiration date for your AppleCare agreement - Apple Support

As shown, it does not show a valid purchase date. For some reason, Apple does not have that information. Follow the information shown and contact Apple Support to fix that. Did you purchase from some place other than Apple or an Authorized Apple reseller?