Bug: Admob+Unity-adapter+subscription -> crash of GatewayException

I've noticed this issue via Crashlytics, here , here and here , meaning on these apps:
https://play.google.com/store/apps/details?id=com.lb.vocalearn
https://play.google.com/store/apps/details?id=com.lb.backup_plus
https://play.google.com/store/apps/details?id=com.lb.get_my_phone_number

To reproduce, install one of these apps (I tested recently on VocaLearn) just purchase subscription. You don't even need to show any ad before. I can add your email to the test users, so that subscription would be for free. I don't know if this will occur on promo codes, and I don't know if it always occur, but it's quite often at least for me.
If it doesn't occur, cancel the subscription, uninstall the app, and when the subscription ends, start the steps again.

I've attached here a video of how to reproduce on VocaLearn app.

The relevant dependencies are:
    implementation("com.google.android.gms:play-services-ads:24.7.0")
    implementation("com.unity3d.ads:unity-ads:4.16.3")
    implementation("com.google.ads.mediation:unity:4.16.3.0")
    implementation("com.android.billingclient:billing-ktx:8.1.0")

Hopefully one will solve this. To me it seems like some Proguard issue of one of the dependencies could solve this, but still shouldn't occur...

Hi,

Thank you for contacting Mobile Ads SDK support team.

As per the logs, it seems like the issue is not related to Mobile Ads SDK. So, we recommend contacting the appropriate team to ensure this issue is resolved.

Thanks,

Feedback
How was our support today?

[2025-11-12 23:57:33Z GMT] This message is in relation to case "ref:!00D1U01174p.!500Ht01vTKlH:ref" (ADR-00339177)

Also, why do you think it's not related to Admob SDK with Unity ?
Isn't Admob responsible of the adapter of Unity , as it's officially supported on the list here:
https://developers.google.com/admob/android/choose-networks
https://github.com/googleads/googleads-mobile-android-mediation

This is what I removed:

Hi,

Thank you for getting back to us.

I understand your concern but please note that our Mobile Ads SDK Support team is not able to test or debug apps distributed through TestFlight or production builds.

I have tested Google Sample Project with the provided dependencies but not able to replicate the reported issue. Could you confirm whether the mentioned issue is reproducible in our sample project after adding the relevant code? If so, please share the following details via reply to author option? for further investigation:

• sample project that replicates the issue

• Steps to reproduce the issue 

• Affected device information if its happening on specific devices

If the file(s) you are looking to share are less than 25mb in total you can attach them to this case on your next reply. If you are having trouble attaching your file to this case or if your file(s) are larger than 25mb, you can share your files with me by performing the following steps:

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[2025-11-13 07:10:53Z GMT] This message is in relation to case "ref:!00D1U01174p.!500Ht01vTKlH:ref" (ADR-00339177)

2. Need to have subscription option

3. Need to have Admob with mediation and Unity adapter and an account there, mapped to various ads.

• Any of these, as it requires a published app on the Play Store that is signed as a release version:

• Steps to reproduce the issue
  After installation, purchase a subscription. Doesn't matter which.
  
  

It occurs on various devices. I already showed a video of this and links on Crashlytics.
What I have though is Pixel 6 with Android 16.