RewardedAd frequently fails with Unable to obtain a JavascriptEngine (errorCode=0) despite WebView being available

[A lan (Alan)]

Hello Google Mobile Ads SDK team,

I’m experiencing a very high failure rate when loading AdMob RewardedAds on Android and would like help understanding the root cause. My app is published and verified on Google Play, using Google Mobile Ads SDK version com.google.android.gms:play-services-ads:24.8.0. Rewarded ads are not completely broken, but the failure rate is extremely high. Based on GA4 analytics, there are 690 RewardedAd load failure events affecting 98 users, with an average of 7.2 failures per user. The overall success rate is about 7%, while approximately 93% of load attempts fail. All failed callbacks consistently return errorCode = 0 (INTERNAL_ERROR) with the message “Unable to obtain a JavascriptEngine.”

I have verified that this is not a basic integration or WebView issue. The WebView provider is available and correct (webview_pkg = com.google.android.webview), and the WebView version is up to date (142.0.7444.171). The error still occurs even when WebView is present and updated. Test ads can load successfully, mediation is disabled (AdMob default only), and the App ID and package name are correctly matched and verified. Since a small percentage of RewardedAd loads do succeed, this does not appear to be a complete configuration or SDK initialization failure.

The failures tend to repeat multiple times on the same users/devices, and the issue is significantly worse for users in Brazil, where more than 80% of RewardedAd load attempts fail. This does not seem limited to a single device model. Given that WebView is available and updated, and that RewardedAds sometimes load successfully, I would like to understand whether this issue could be related to Rewarded ad JavaScript runtime initialization, Google Play services / Ads runtime availability, regional or device-level restrictions, or any app-level or account-level ad serving limitations.

Any guidance on how to further diagnose or mitigate the “Unable to obtain a JavascriptEngine” error for RewardedAds would be greatly appreciated. Thank you.