[Bug] Mobile OTP not sent

### [REQUIRED] Please fill in the following fields:

* Pre-built SDK from the [website](https://firebase.google.com/download/cpp) or open-source from this repo: from Website
* Firebase C++ SDK version: 11.3.0
* Problematic Firebase Component: Auth
* Other Firebase Components in use: Auth
* Platform you are using the C++ SDK on: Android
* Platform you are targeting: Android, iOS

### [REQUIRED] Please describe the issue here:

I am using QT framework along with Firebase SDK version (11.3) to get PhoneNumber Authentication OTP. I am giving correct format of 10 digit Phone number with "+countrycode". I follow the same procedure mentioned in the Firebase documenation for C++.

#### Steps to reproduce:

When i called the below VerifyPhoneNumber function, the OnCodeSent() function being called and it is confirming that the phone_listener is working fine. However, I am not able to receive the OTP to the mobile Number. I tried with nearly 3 phone numbers and same issue exists. Also, i do not get any error from Firebase as a Notification in the console.

So, i am clueless where it is going wrong. I have already done the project settings in Firebase and enable phoneNumber authentication.

The code is given below

#### Relevant Code:

```
// TODO(you): code here to reproduce the problem

localmobile = "+918939608135";
PhoneListener phone_listener;
firebase::auth::PhoneAuthOptions options;
options.timeout_milliseconds = 30;
options.phone_number = localmobile.toUtf8().constData();
qDebug()<< "options.phone_number"<< options.phone_number;
firebase::auth::PhoneAuthProvider& phone_provider = firebase::auth::PhoneAuthProvider::GetInstance(m_auth);
phone_provider.VerifyPhoneNumber(options, &phone_listener);
```

Inizia con la chiamata a Firebase Auth PhoneAuthProvider::VerifyPhoneNumber e i relativi callback PhoneListener, utilizzando i target Android e iOS descritti nel report. Controlla le impostazioni documentate del progetto per l’autenticazione telefonica e il percorso OnCodeSent; il lavoro è completato quando l’OTP mancante viene riprodotto con un caso di test completo e viene identificata una causa risolvibile nell’SDK o nella configurazione.

Scritto dal modello di indicizzazione a partire dal testo della issue.