I am using Firebase Notification for my car Manager Application for android. all code works fine if i set isMinifyEnabled = false but when set isMinifyEnabled = true like this

 buildTypes {
        relese {
            isShrinkResources = true
            isMinifyEnabled = true
            proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
        }
    }

then Notification doesn’t show.

my proguard rules are

-keep class com.gixcar.manager.model.UserModel { *; }
-keep class com.gixcar.manager.model.NotificationModel { *; }
-keep class com.gixcar.manager.utility.NotificationUtils { *; }
-keep class com.google.firebase.** { *; }
-keep class com.google.firebase.messaging.** { *; }
-keep class com.google.firebase.iid.** { *; }
-keep class com.google.firebase.** { *; } 
-dontwarn com.google.firebase.**
-dontwarn com.google.android.gms.**
-keepattributes *Annotation*

Manifiest.xml

<Application>
 <service
            android:name=".service.NotificationService"
            android:exported="false">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT" />
            </intent-filter>
        </service>
</Application>

Here is show notification method using Okhttp library

 private static String getAccessToken() {
        String AUTH_TOKEN = "{n" +
                "  "type": "service_account",n" +
                "  "project_id": "gix-car",n" +
                "  "private_key_id": "73263fef7e98e3e52a3aae2a84ec101a8d46dc17",n" +
                "  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvwIBADANBgkqhkiG9w0jhgyutuygbhjgyikuhkjhuuinjyiuhjhi8ulkjugh40QjfcI3UVcMSlHO\nHUV0Cv/zx3YGi5/Pc+SAoskrU8CzQbC6+PGVKOQrK3ZkC++/C4w1ZQN1Wz1XlVzG\nVoieKhKXFkje1oKILWhiD3gUmEq/u+rdRILQYJEomR0ioC+89M6QOYuiIhuPwwgW\n3zm3qJZTAgMBAAx4\nZt1KRmGxUK4RPMCzL6hjLhsypA==\n-----END PRIVATE KEY-----\n",n" +
                "  "client_email": "firebase-adminsdk@example_email",n" +
                "  "client_id": "102543545454545345",n" +
                "  "auth_uri": "https://accounts.google.com/o/oauth2/auth",n" +
                "  "token_uri": "https://oauth2.googleapis.com/token",n" +
                "  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",n" +
                "  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/firebase-example_gserviceaccount.com",n" +
                "  "universe_domain": "googleapis.com"n" +
                "}n";

        try {
            InputStream stream = new ByteArrayInputStream(AUTH_TOKEN.getBytes());
            String firebaseScope = "https://www.googleapis.com/auth/firebase.messaging";
            GoogleCredentials credentials = GoogleCredentials.fromStream(stream).createScoped(Lists.newArrayList(firebaseScope));
            credentials.refresh();
            return credentials.getAccessToken().getTokenValue();
        } catch (IOException e) {
            Log.e("FCM AccessToken", "Access token failed: " + e);
            return null;
        }
    }


    public static void sendNotification(String mob_no, String title, String msg, String data, Uri imageUrl) {
        FirebaseUtil.userInfo(mob_no).get().addOnCompleteListener(task -> {
            if (task.isSuccessful()) {
                String token = task.getResult().getString("userToken");
                try {
                    JSONObject combineObject = new JSONObject();
                    JSONObject notification = new JSONObject();
                    JSONObject messageObj = new JSONObject();
                    JSONObject dataObj = new JSONObject();
                    notification.put("title", title);
                    notification.put("body", msg);
                    notification.put("image", imageUrl);
                    dataObj.put("locationData", data);

                    messageObj.put("token", token);
                    messageObj.put("notification", notification);
                    messageObj.put("data", dataObj);
                    combineObject.put("message", messageObj);
                    callApi(combineObject);
                } catch (Exception e) {
                    Log.e("notification error", "sendNotification: " + e.getLocalizedMessage());
                }
            }
        });
    }

    private static void callApi(JSONObject jsonObject) {
        MediaType jsonPayload = MediaType.get("application/json");
        OkHttpClient client = new OkHttpClient();
        String url = "https://fcm.googleapis.com/v1/projects/gix-car/messages:send";
        RequestBody body = RequestBody.create(jsonObject.toString(), jsonPayload);
        Request request = new Request.Builder()
                .url(url)
                .addHeader("Authorization", "Bearer " + getAccessToken())
                .post(body)
                .build();
        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(@NonNull Call call, @NonNull IOException e) {
                Log.e("FCM Error", "Notification failed: " + e);
            }

            @Override
            public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
                if (response.isSuccessful()) {
                    Log.e("FCM Success", "Notification sent successfully: " + response.body().string());
                } else
                    Log.e("FCM Error", "Notification failed: " + response.body().string());
            }
        });
    }

I have already tried by Adding Proguard rules but not working
showing this error Access token failed: com.google.auth.oauth2. GoogleAuthException: Error getting access token for service account: 400 Bad Request                                                                                                     POST https://oauth2.googleapis. com/ token