Hi there,
I reckon you're making use of Android Studio? If so, Could you maybe repeat the following steps (if you haven't already) and try to build your app again:
Run npm install
(for NPM v7 and above run npm install --legacy-peer-deps
) in the app root to install the required dependencies.
Run npm run configure
to apply the configuration from the Mendix Native Mobile Builder to the app.
Open Android Studio.
Select the <Native Template root>/android
as the entry point for the app.
I don't know all that much about the Native aspect, but it sounds like a missing dependency.
I really hope this helps.