Crashlytics Mapping files not getting generated

I have enabled proguard using minifyEnabled true and trying to create build from jenkins. But while creating apk from jenkins I am getting following build error.

> Task :app:packageUat
> Task :app:uploadCrashlyticsMappingFileUat FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:uploadCrashlyticsMappingFileUat'.
> Crashlytics could not find the resource file generated by Google Services. You may need to execute the :process<Variant>GoogleServices Task. Please check your Firebase project configuration (https://firebase.google.com/docs/android/setup). 

I am using FCM and Crashlytics Google services in my application. I have not included google-service.json but initializing runtime. Here is firebase initialization code :

FirebaseApp.initializeApp(mAppContext, new FirebaseOptions.Builder()
            .setProjectId(BuildConfig.PROJECT_ID)
            .setApiKey(BuildConfig.API_KEY)
            .setApplicationId(BuildConfig.FCM_APPLICATION_ID)
            .setGcmSenderId(BuildConfig.GCM_SENDER_ID)
            .build());

    FirebaseCrashlytics.getInstance().setCrashlyticsCollectionEnabled(true);

Following command I am using on jenkins to create build :

clean
assemble${Build}

Here is my uat build configuration :

uat {
        minifyEnabled true
        shrinkResources true
        signingConfig signingConfigs.uat
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        buildConfigField "String", 'API_KEY', API_KEY
        buildConfigField "String", 'FCM_APPLICATION_ID', FCM_APPLICATION_ID
        buildConfigField "String", 'PROJECT_ID', PROJECT_ID
        buildConfigField "String", 'GCM_SENDER_ID', GCM_SENDER_ID

    }

I can not include google-service.json in my project because of security issue. Is there anything I am missing?

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