Данные с сервера не грузятся , вместо них показывает null

Не знаю в чем проблема , при запуске приложения ,показывает null,видимо данные с сервера не пришли, использую retrofit,помогите пожалуйста ,заранее спасибо)
Main Activity

`class MainActivity : AppCompatActivity() {

private lateinit var viewModel: MainViewModel
private lateinit var GET:SharedPreferences
private lateinit var SET:SharedPreferences.Editor
private lateinit var binding:ActivityMainBinding

val API: String = "34ae534ae4ff9829f963590e080ea518"
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding =ActivityMainBinding.inflate(layoutInflater)
    val view = binding.root
    setContentView(view)
    //setContentView(R.layout.activity_main)
    GET=getSharedPreferences(packageName, MODE_PRIVATE)
    SET=GET.edit()

    viewModel = ViewModelProvider(this).get(MainViewModel::class.java)

    var cName =GET.getString("cityName","ankara")
    binding.edtCityName.setText(cName)

    viewModel.refreshData(cName!!)

    getLiveData()
    binding.swipeRefreshLayout.setOnRefreshListener {
        binding.llDataView.visibility=View.GONE
        binding.tvError.visibility=View.GONE
        binding.pbLoading.visibility=View.GONE

        var cityName = GET.getString("cityName",cName)
        binding.edtCityName.setText(cityName)
        viewModel.refreshData(cityName!!)
        binding.swipeRefreshLayout.isRefreshing=false
    }
    binding.imgSearchCityName.setOnClickListener{
        val cityName =binding.edtCityName.text.toString()
        SET.putString("cityName",cityName)
        SET.apply()
        viewModel.refreshData(cityName!!)
        getLiveData()
    }

}

private fun getLiveData() {
    viewModel.weather_data.observe(this, Observer { data ->
    data.let {
        binding.llDataView.visibility= View.VISIBLE
        binding.pbLoading.visibility=View.GONE

        binding.tvDegree.text = data?.main?.temp.toString()
        binding.tvCountryCode.text = data?.sys?.country.toString()
        binding.tvCityName.text = data?.name.toString()
        binding.tvHumidity.text = data?.main?.humidity.toString()
        binding.tvSpeed.text = data?.wind?.speed.toString()
        binding.tvLat.text =data?.coord?.lat.toString()
        binding.tvLon.text = data?.coord?.lon.toString()

        Glide.with(this).load("http://openweathermap.org/img/wn/"+data?.weather?.get(0)?.icon+"[email protected]")
            .into(binding.imgWeatherIcon)
    }
    })
    viewModel.weather_load.observe(this, Observer { load->
        load.let {
            if(it == true){
               binding.pbLoading.visibility=View.VISIBLE
               binding.tvError.visibility=View.GONE
               binding.llDataView.visibility=View.GONE
        }else{
            binding.pbLoading.visibility=View.GONE

            }
        }
    })
    viewModel.weather_error.observe(this, Observer { error->
        error?.let {
            if(it){
                binding.tvError.visibility = View.VISIBLE
                binding.llDataView.visibility = View.GONE
                binding.pbLoading.visibility = View.GONE
            }else{
                binding.tvError.visibility =View.GONE
            }
        }
    })
}

} `
* Dependencies*

`implementation 'android.arch.lifecycle:extensions:1.1.1'
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.2'
implementation 'com.google.android.material:material:1.6.1'
implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
implementation 'android.arch.lifecycle:extensions:1.1.1'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

//for refresh
implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.1.0'
//life cycle

//retrofit
implementation "com.squareup.retrofit2:retrofit:2.3.0"
implementation "com.squareup.retrofit2:converter-gson:2.3.0"
implementation 'com.squareup.retrofit2:adapter-rxjava2:2.9.0'
//rxjava
implementation"io.reactivex.rxjava2:rxjava:2.1.1"
implementation "io.reactivex.rxjava2:rxandroid:2.1.1"
//pictures
implementation "com.github.bumptech.glide:glide:4.12.0"

implementation "androidx.legacy:legacy-support-v4:1.0.0"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.4.3"`

* WeatherARI*

    ` package com.example.weather30.service

    import com.example.weather30.model.WeatherModel
    import io.reactivex.Single
    import retrofit2.http.GET
    import retrofit2.http.Query

    //https://api.openweathermap.org/data/2.5/weather?                     
   q=Omsk&units=metric&appid=34ae534ae4ff9829f963590e080ea518
   interface WeatherAPI {
   @GET("data/2.5/weather?&units=metric&appid=34ae534ae4ff9829f963590e080ea518")
   fun getData(
      @Query("q") cityName:String
          ):Single<WeatherModel>

}`
weatherService

     `//https://api.openweathermap.org/data/2.5/weather? 
     q=Omsk&units=metric&appid=34ae534ae4ff9829f963590e080ea518
    class WeatherAPIservice {
     private val BASE_URL ="https://api.openweathermap.org/"
       private  val api =  Retrofit.Builder()
    .baseUrl(BASE_URL)
    .addConverterFactory(GsonConverterFactory.create())
    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
    .build()
    .create(WeatherAPI::class.java)
    fun getDataService(cityName:String):Single<WeatherModel>{
    return api.getData(cityName)
}

}`

weather.viewmodel

   ``` class MainViewModel: ViewModel(){
private val WeatherAPIservice = WeatherAPIservice()
private val disposable =CompositeDisposable()

val weather_data = MutableLiveData<WeatherModel>()
val weather_error = MutableLiveData<Boolean>()
val weather_load = MutableLiveData<Boolean>()

fun refreshData(cityName: String){
    getDataFromAPI(cityName)
    //getDataFromLocal()
}

private fun getDataFromAPI(cityName:String) {
    weather_load.value =true
    disposable.add(
        WeatherAPIservice.getDataService(cityName)
            .subscribeOn(Schedulers.newThread())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribeWith(object: DisposableSingleObserver<WeatherModel>(){
                override fun onSuccess(t: WeatherModel) {
                    weather_data.value=t
                    weather_error.value=false
                    weather_error.value=false

                }

                override fun onError(e: Throwable) {
                   weather_error.value=true
                    weather_load.value=false
                }

            })
    )
}
}```