Error: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path

First Check your server response is valid JSON or Not if not make it proper

To check the resposne you can add loggingInterceptor for OkHttpClient

OkHttpClient client = new OkHttpClient.Builder()
.addInterceptor(new LoggingInterceptor()).build();

static class LoggingInterceptor implements Interceptor {
@Override
public Response intercept(Interceptor.Chain chain) throws IOException {
Request request = chain.request();

long t1 = System.nanoTime();
Log.v("Request ",String.format("Sending request %s on %s%n%s",
request.url(), chain.connection(), request.headers()));

Response response = chain.proceed(request);

long t2 = System.nanoTime();
Log.v("Request ",String.format("Received response for %s in %.1fms%n%s",
response.request().url(), (t2 - t1) / 1e6d, response.headers()));

final String responseString = new String(response.body().bytes());

Log.v("Request ","Response: " + responseString);

return response.newBuilder()
.body(ResponseBody.create(response.body().contentType(), responseString))
.build();
}}

If every thing fine add GsonConverter with below code

GsonBuilder gsonBuilder=new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
gsonBuilder.setLenient();

Finally Retrofit object creation should be like below

Retrofit.Builder()
        .addConverterFactory(GsonConverterFactory.create(gsonBuilder.create()))
      .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
        .baseUrl(ApiCall.BASE_IRL)
        .client(client)
        .build();