SKAN / AdAttributionKit Development Postback Not Triggering

We’re testing SKAN postbacks via AdAttributionKit but aren’t receiving any requests on our server even after generating development impressions and triggering a postback.

Setup:

• Domain: https://linkrunner-skan.com
• Configured in Info.plist as:

<key>NSAdvertisingAttributionReportEndpoint</key>
<string>https://linkrunner-skan.com</string>

<key>AttributionCopyEndpoint</key>
<string>https://linkrunner-skan.com</string>

• Apple automatically appends the .well-known paths:

  • /.well-known/private-click-measurement/report-attribution/
  • /.well-known/skadnetwork/report-attribution/

• ATS diagnostics for the domain: PASS for all tests (TLS 1.0–1.3, PFS disabled, arbitrary loads allowed, etc.)

• Both .well-known paths are publicly accessible and return 200 OK

Testing Flow:

1. Enabled Developer → AdAttributionKit Developer Mode on iOS (15+)

2. Followed Apple’s official guide: Testing AdAttributionKit with Developer Mode

3. Generated test impression using:

   • createAdAttributionKitDevelopmentImpression implemented in SKANManager.swift

4. Called Postback.updateConversionValue with lockPostback: true

5. Created Development Postback from Developer Settings

6. Waited 30+ minutes while intercepting server requests (proxy + backend logs)

What We’ve Tried So Far:

• Confirmed ATS compliance with nscurl --ats-diagnostics (all PASS)
• Verified .well-known paths are accessible publicly without redirects
• Tested endpoints manually with a POST request – server responds 200 OK
• Confirmed Info.plist entries exactly match Apple’s required keys
• Double-checked iOS device is running iOS 15+ with Developer Mode enabled
• Repeated test flow multiple times with fresh impressions and postbacks
• Waited up to 1 hour for postback (in case of delays)

Issue: No POST requests are being received from Apple to either .well-known endpoint, even though the setup appears correct and ATS tests pass.

References Used:

• Configuring an Advertised App
• Generating JWS Impressions

Question: Has anyone faced a similar issue where AdAttributionKit Development Postbacks are not firing despite correct Info.plist setup, ATS compliance, and reachable .well-known endpoints? Any insight into possible missing configuration steps or testing nuances would be greatly appreciated.