Uno and Nano

Hi, I appreciate this. It's exactly what I need. But I have some issues. Codes work like charm on mega but I cant say same things for uno and nano. I tried code below and use built in led for test. Its work on mega but not uno or nano. Can you help me I couldnt understand What I did wrong.

Ps sorry for language

/*
 * Test FlySky IBus interface on an Arduino Mega.
 *  Connect FS-iA6B receiver to Serial1.

 */
 
#include "FlySkyIBus.h"

void setup() 
{
  Serial.begin(115200);
  IBus.begin(Serial);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() 
{

  IBus.loop();

    if (IBus.readChannel(0) >= 1500)
    {
    digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(1000);     
    }
    else
    {
    digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(200); 
    digitalWrite(LED_BUILTIN, LOW);
    delay(200); 
        digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(200); 

    
    }
  
  Serial.println("CH1 ") ;
  Serial.println(IBus.readChannel(0));
//  Serial.println("CH2 ") ;
//  Serial.println(IBus.readChannel(1), DEC);
//  Serial.println("CH3 ") ;
//  Serial.println(IBus.readChannel(2), DEC); 
//  Serial.println("CH4 ") ;
//  Serial.println(IBus.readChannel(3), DEC); 
//  Serial.println("CH5 ") ;
//  Serial.println(IBus.readChannel(4), DEC);
//  Serial.println("CH6 ") ;
//  Serial.println(IBus.readChannel(5), DEC);
//  Serial.println("CH7 ") ;
//  Serial.println(IBus.readChannel(6), DEC); 
//  Serial.println("CH8 ") ;
//  Serial.println(IBus.readChannel(7), DEC);
//  Serial.println("CH9 ") ;
//  Serial.println(IBus.readChannel(8), DEC); 
//  Serial.println("CH10 ") ;
//  Serial.println(IBus.readChannel(9), DEC);
  //  delay(3000);
}