AdMob Test Ads Fail (Error 3 & Null ResponseInfo) While Live Ads Work

Saffron

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Oct 13, 2025, 8:56:55 AMOct 13

to Google Mobile Ads SDK Developers

Hello Experts,

We are facing a persistent issue where test ads fail 100% of the time, but live ads serve perfectly. We have exhausted all standard troubleshooting and are seeking expert guidance.

The Core Problem

Test Ads Fail: All formats return Error Code 3 (No Fill). This happens with both Google's sample ad units and our own units with a registered test device.
Live Ads Work: The exact same code implementation successfully loads and displays live ads when the test configuration is removed.
The Critical Clue: For every failed test ad, loadAdError.getResponseInfo() returns null. We get no Response ID or any diagnostic auction data, which is highly unusual for a standard "No Fill" error.

Key Log Output for Failed Test Ad

FAILED TO LOAD (INTERSTITIAL) Code: 3 (NO_FILL) ║ Domain: com.google.android.gms.ads ║ Message: No fill. ║ Response ID: N/A (Because ResponseInfo is null)

What We've Ruled Out

Mediation: Our setup is 100% pure AdMob. All third-party mediation SDKs and dependencies have been completely removed.
UMP/GDPR: Our User Messaging Platform SDK is correctly integrated and the consent flow completes successfully before any ad requests are made.
Basic Setup: Live ads are working, which confirms our core SDK initialization, ad lifecycle management, and UI code are correct.
Client-Side Cache: We have performed aggressive cleaning, including:
- Deleting all build and .catch folders.
- Manually verifying all libs folders are empty.
- Clearing the cache and storage for both our app and Google Play Services on the device.
- Resetting the device's Advertising ID.
Account Issues: Our AdMob account is 3+ years old and has no policy violations.

Given that live ads work and UMP is correctly implemented, why would test ad requests be the only ones failing with a null ResponseInfo?

What further steps can we take, or what specific information can we capture, to diagnose why test ad requests are being treated (No Fill) and result in a completely empty response?