Network request failed error in real android device once Register using API

** I am trying to build a registration page in react-native which sends the data to an API. Whenever I try filling the form and sending the request, the emulator works fine but real android device shows a Network Request Failed error. I have read almost all related answers but none of them seem to help me. I am working with Android 7.0 API level 24. The code attached below.I have enabled internet permission in manifest file.**

fetchRegister(){
    var object = {
      method: 'POST',
      headers: {
        'Accept': 'application/json',
        'Content-Type': 'application/json'
      },
      body:JSON.stringify( {
        "phone_number": this.state.contactNumber,
        "password": this.state.password,
      })
  };


  fetch('https://example.com/chatapp/web/registrations.php',object)
    .then((response) => response.json())
    .then((responseText) => {


        if(responseText.status == '200'){
              this.setState({
                registrationSuccessfull:true
              })

            var { navigate} = this.props.navigation;
            setTimeout(() => {
              navigate("Login",{screen: "Login"});
            }, 3000);
        }else if(responseText.status == '405'){
            this.setState({
              registeredAlready:true,
            });
        }
    })
    .catch((error) => {
        console.error(error);
    });
  }