Sim7600E kc868_A4S GSM SIM Internet Is not working - 4G and 3G Enabled

[venuakil2]

Hi, I am Sim7600E kc868_A4S Model to call website URL after Internet activation. 

SIM Yellow Light is blinking. 

SIM call and SMS are working. But, Internet is not working. I have changed SIM Provider APN details


#include <HardwareSerial.h>
// Define SIM7600 UART
#define MODEM_RX 13   // Connect to SIM7600 TX
#define MODEM_TX 15   // Connect to SIM7600 RX
HardwareSerial sim7600(1);  // Use UART1
const char* APN = "du";    // Set your network APN
const char* USER = "";     // Usually blank
const char* PASS = "";     // Usually blank
void setup() {
  Serial.begin(115200);           // USB serial
  sim7600.begin(115200, SERIAL_8N1, MODEM_RX, MODEM_TX); // UART1
  delay(5000);  // Give time to power up
  Serial.println("Initializing SIM7600...");
  // Disable echo for clean output
  sendATCommand("ATE0", "OK", 1000);
  // Basic check
  if (!retryCommand("AT", "OK", 2000, 3)) {
    Serial.println("SIM7600 not responding!");
    while (1);
  }
  // SIM card check
  if (!sendATCommand("AT+CPIN?", "READY", 2000)) {
    Serial.println("SIM Card not ready!");
    while (1);
  }
  // Set LTE-only mode
  sendATCommand("AT+CNMP=38", "OK", 3000);
  sendATCommand("AT+CMNB=1", "OK", 3000);
  // Set APN
  String apnCmd = "AT+CGDCONT=1,\"IP\",\"" + String(APN) + "\"";
  sendATCommand(apnCmd.c_str(), "OK", 3000);
  // Attach to network
  if (!sendATCommand("AT+CGATT=1", "OK", 10000)) {
    Serial.println("Failed to attach to network!");
    while (1);
  }
  // Activate PDP
  if (!sendATCommand("AT+CGACT=1,1", "OK", 10000)) {
    Serial.println("Failed to activate PDP!");
    while (1);
  }
  // Show IP
  printIPAddress();
}
void loop() {
  // Optional: monitor SIM7600 data or implement HTTP
}
// ========== AT COMMAND HELPERS ==========
bool sendATCommand(const char* cmd, const char* expected, uint32_t timeout) {
  sim7600.flush();
  sim7600.println(cmd);
  Serial.print(">> "); Serial.println(cmd);
  uint32_t start = millis();
  String response;
  while (millis() - start < timeout) {
    while (sim7600.available()) {
      char c = sim7600.read();
      Serial.write©;
      response += c;
      if (response.indexOf(expected) != -1) {
        return true;
      }
    }
  }
  Serial.println("\n!! Timeout or Unexpected response:");
  Serial.println(response);
  return false;
}
bool retryCommand(const char* cmd, const char* expected, uint32_t timeout, int retries) {
  for (int i = 0; i < retries; i++) {
    if (sendATCommand(cmd, expected, timeout)) return true;
    delay(1000);
  }
  return false;
}
void printIPAddress() {
  Serial.println("Checking IP with AT+CGPADDR=1...");
  sim7600.println("AT+CGPADDR=1");
  delay(1000);
  String response;
  while (sim7600.available()) {
    char c = sim7600.read();
    Serial.write©;
    response += c;
  }
  int ipStart = response.indexOf(",\"") + 2;
  int ipEnd = response.indexOf("\"", ipStart);
  if (ipStart > 1 && ipEnd > ipStart) {
    String ip = response.substring(ipStart, ipEnd);
    Serial.print("Assigned IP: ");
    Serial.println(ip);
  } else {
    Serial.println("No IP Address Assigned");
  }
}

OutPut  
13:57:40.249 -> >> AT
13:57:42.215 -> !! Timeout or Unexpected response:
13:57:49.212 -> SIM7600 not responding!


Note : SIM calling is working 
Note 2: SIM SMS are working.
Only Internet is not activated. I have to call website URL after Internet connected.