La llamada de API de actualización recibe "HTTP FALLIDO: java.io.IOExcepción: Cancelado"

No puedo entender por qué está sucediendo esto. Ninguno de los callbacks de rx (onCompleted (), onError (), onNext ()) no se activa con mi llamada. Lo único que recibo es esta salida okhttp:

D/OkHttp: --> GET https://api.privatbank.ua/p24api/exchange_rates?json=true&date=20.11.2016 http/1.1
D/OkHttp: --> END GET
D/OkHttp: <-- HTTP FAILED: java.io.IOException: Canceled

Módulo de actualización:

@Module
public class RestModule {

    @Provides
    @Singleton
    public HttpLoggingInterceptor providesHttpLogginInterceptor() {
        return new HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY);
    }

    @Provides
    @Singleton
    public OkHttpClient providesOkHttpClient(@NonNull HttpLoggingInterceptor loggingInterceptor) {
        return new OkHttpClient.Builder()
            .addInterceptor(loggingInterceptor)
            .connectTimeout(ConstantsManager.CONNECTION_TIME_OUT, TimeUnit.SECONDS)
            .readTimeout(ConstantsManager.READ_TIME_OUT, TimeUnit.SECONDS)
            .build();
    }

    @Provides
    @Singleton
    public Gson providesGson() {
        return new GsonBuilder().create();
    }

    @Provides
    @Singleton
    public Retrofit providesRetrofit(@NonNull OkHttpClient okHttpClient, @NonNull Gson gson) {
        return new Retrofit.Builder()
            .baseUrl(ConstantsManager.BASE_URL)
            .client(okHttpClient)
            .addConverterFactory(SimpleXmlConverterFactory.create())
            .addConverterFactory(GsonConverterFactory.create(gson))
            .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
            .build();
    }

    @Provides
    @Singleton
    public PrivatbankApi providesPrivatbankApi(@NonNull Retrofit retrofit) {
        return retrofit.create(PrivatbankApi.class);
    }
}

Interfaz API:

public interface PrivatbankApi {

    @GET
    Observable<CurrentRates> loadCurrentRates(@NonNull @Url String url);

    @GET("exchange_rates")
    Observable<DateRates> loadDateRates(@NonNull @Query("json") Boolean json, @NonNull @Query("date") String date);

}

Suscripción:

subscription = dataManager.loadDateRates(date)
                .subscribeOn(Schedulers.io())
                .doAfterTerminate(() -> {
                })
                .subscribe(dateRates -> {
                    // My code here...
                }, throwable -> {
                    Timber.e(throwable, "Error while loading data occurred!");
                });

Por cierto, ambas llamadas obtienen el mismo error:

D/OkHttp: --> GET https://privat24.privatbank.ua/p24/accountorder?oper=prp&PUREXML&apicour&country=ua http/1.1
D/OkHttp: --> END GET
D/OkHttp: <-- HTTP FAILED: java.io.IOException: Canceled
D/OkHttp: --> GET https://api.privatbank.ua/p24api/exchange_rates?json=true&date=20.11.2016 http/1.1
D/OkHttp: --> END GET
D/OkHttp: <-- HTTP FAILED: java.io.IOException: Canceled