Firebase Phone Authentication in Flutter[Android] App not working

Question

[Issue only exists in Release Mode] User is getting an OTP, but the screen is not moving forward I am trying to use firebase phone authentication, but is met with the following error:

    E/flutter ( 9235): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception:        [firebase_auth/unknown] null
    E/flutter ( 9235): #0      AuthProvider.signInWithPhone.<anonymous closure> (package:my_cube/services/auth.dart:62)
    E/flutter ( 9235): #1      MethodChannelFirebaseAuth.verifyPhoneNumber.<anonymous closure> (package:firebase_auth_platform_interface/src/method_channel/method_channel_firebase_auth.dart:663)
    E/flutter ( 9235): #2      _RootZone.runUnaryGuarded (dart:async/zone.dart:1594)
    E/flutter ( 9235): #3      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:339)
    E/flutter ( 9235): #4      _BufferingStreamSubscription._add (dart:async/stream_impl.dart:271)
    E/flutter ( 9235): #5      _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:123)
    E/flutter ( 9235): #6      _HandleErrorStream._handleData (dart:async/stream_pipe.dart:253)
    E/flutter ( 9235): #7      _ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:153)
    E/flutter ( 9235): #8      _RootZone.runUnaryGuarded (dart:async/zone.dart:1594)
    E/flutter ( 9235): #9      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:339)
    E/flutter ( 9235): #10     _DelayedData.perform (dart:async/stream_impl.dart:515)
    E/flutter ( 9235): #11     _PendingEvents.handleNext (dart:async/stream_impl.dart:620)
    E/flutter ( 9235): #12     _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:591)
    E/flutter ( 9235): #13     _microtaskLoop (dart:async/schedule_microtask.dart:40)
    E/flutter ( 9235): #14     _startMicrotaskLoop (dart:async/schedule_microtask.dart:49)

Logcat: throws above error, and following error before that: [SmsRetrieverHelper] SMS verification code request failed: unknown status code: 17499 Instantiation of JsonResponse failed! class com.google.android.gms.internal.firebase-auth-api.o2

What happens: I enter phone number,and press the button, I am taken to a web page for recaptcha verification. After that, returns to app and then the above error is thrown.I do recieve otp though Function I use to pass phone number:

void sendPhoneNumber() {
    final AuthProvider authService = Provider.of<AuthProvider>(
        context, listen: false);
    String phoneNumber = phoneController.text.trim();
    FirebaseAuth.instance.setSettings(appVerificationDisabledForTesting: false);

    authService.signInWithPhone(context, "+${country.phoneCode}$phoneNumber");
  }

SignInWithPhone function:

signInWithPhone(BuildContext context, String phoneNumber,) async {
    ToastContext().init(context);
    try {
      await _auth.verifyPhoneNumber(
          phoneNumber: phoneNumber,

          verificationCompleted:
              (PhoneAuthCredential phoneAuthCredential) async {
                await _auth.signInWithCredential(phoneAuthCredential);
                Toast.show("Verification Completed", duration: Toast.lengthShort, gravity:  Toast.bottom);
      },
          verificationFailed: (FirebaseAuthException error) {
            Toast.show('$error', duration: Toast.lengthShort, gravity:  Toast.bottom);
            throw FirebaseAuthException(code: error.code, message: error.message);
          },
          codeSent: (verificationId, forceResendingToken) {
            Toast.show("Code Sent", duration: Toast.lengthShort, gravity:  Toast.bottom);
            Navigator.push(
              context,
              MaterialPageRoute(
                builder: (context) => Otp(verificationId: verificationId),
              ),
            );
          },
          codeAutoRetrievalTimeout: (verificationId) {});
    } on FirebaseAuthException catch (e) {
      showSnackBar(context, e.message.toString());
      Toast.show('$e', duration: Toast.lengthLong, gravity:  Toast.bottom);
      print(e.message);
    }
  }

I am recieving an otp, but cannnot enter it as they are in different pages and navigation is not working. If it is indeed due to missing PlayIntegrity token, Please metion how to solve it, for a flutter app. I am a beginner.

Things I have tried: Verified that SHA-1 Hash is same in firebase and project. Enabled Play Integrity API[Did not add any code related to it in app, don't know how to do it for an app that is not in playstore.] added latest googelservices.json to app