Had this issue while deploying Firebase Crashlytics to one of my apps. Everything was set up as per Firebase instructions. A test crash while the app was deployed via Xcode was reported and logged in Firebase Crashlytics console as expected.

However, after deploying the app to the App Store (or TestFlight) and triggering the same crash nothing was getting reported.

After some troubleshooting, I found that the issue was affecting one of my two iPhones and not affecting the other one (regardless of whether the app was deployed via Apple or Xcode). Further digging into Crashlytics debug logs revealed that Crashlytics was having issues accessing some of the Firebase domains on the affected device.

This very quickly lead me to the culprit – the affected iPhone had Next DNS web filtering service running, which was blocking some domains required for Crashlytics. After disabling Next DNS, everything started functioning as expected.

February 2025
Oxford, Oxfordshire