How to have flutter webhook receive promo code usage from iOS?

I made a promo code purchase using the app store url method below, but the webhook did not pick up that purchase even though i have uploaded my App Store Connect API Key and my In-App Purchase Config Key in the settings. Any guidance on how to get the webhook to trigger if they go through this route? Thanks!

https://apps.apple.com/redeem?ctx=offercodes&id={apple_app_id}&code={code}