Install-validation postback is not received

Hi,

We have Apple Search Ads for promoting our app.

We are able fetch attribution records of those ads using AAAttribution inside app and send to our server and it is working fine.

Now, we would like to receive Install-validation postbacks by setting NSAdvertisingAttributionReportEndpoint into our domain name and configured the server to receive HTTPS POST messages as per the instruction provided in the below link.

Steps done

1. Set NSAdvertisingAttributionReportEndpoint into our domain name
2. Our server configured the server to receive HTTPS POST messages
3. Made sure that updatePostbackConversionValue is called while app is launched.

https://developer.apple.com/documentation/bundleresources/information_property_list/nsadvertisingattributionreportendpoint

In our live app, we are keep getting attribution records using AAAttribution inside our app and sending them to our server. It is working fine now.

But we did not receive any Install-validation postback yet into the URL provided in NSAdvertisingAttributionReportEndpoint.

To troubleshoot this, i clicked Apple Search Ad of our app in App Store, i installed our app and opened it and in the console i can see the below error message.

Error updating install attribution pingback for app: <OUR_APP_ID>, error: Error Domain=ASDErrorDomain Code=1208 "SKAdNetwork: No pingbacks found while attempting to register/ update." UserInfo={NSLocalizedDescription=SKAdNetwork: No pingbacks found while attempting to register/update.}, result: 0

I have attached console log for your reference.

Is there any step i am missing to receive Install-validation postback in our server?

Is there any way to validate domain name provided in nsadvertisingattributionreportendpoint so that we can check if any server configuration issue?

Please advise on getting Install-validation postback in our server, Thank you.